Communication control method and user device

Abstract

A communication control method according to one aspect of the present invention is used in a cellular communication system. The communication control method includes: a step in which a relay node reports an offset value for a mobile relay node; and a step in which a user device executes an intra frequency cell reselection procedure by using the offset value for the mobile relay node.

Description

Communication Control Method

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

[0002] The Third Generation Partnership Project (3GPP), a standardization project for cellular communication systems, is considering the introduction of a new relay node called an Integrated Access and Backhaul (IAB) node (see, for example, Non-Patent Document 1). One or more relay nodes intervene in communication between a base station and a user device and relay this communication.

[0003] 3GPP TS 38.300 V17.2.0 (2022-09)

[0004] A communication control method according to a first aspect is a communication control method for use in a cellular communication system, the communication control method comprising: a relay node broadcasting a mobile relay node offset value; and a user equipment performing an intra-frequency cell reselection procedure using the mobile relay node offset value.

[0005] A communication control method according to a second aspect is a communication control method for use in a cellular communication system, the communication control method comprising the steps of: receiving, by a user equipment, from a cell, High Speed ​​Dedicated Network (HSDN) cell information indicating that the cell is an HSDN cell; and mobile relay node cell type information indicating that the cell is a cell of the mobile relay node. The communication control method also comprises the steps of: performing, by the user equipment, an inter-frequency cell reselection procedure when in a low-motion state, without regarding the cell as a lowest-priority cell.

[0006] FIG. 1 is a diagram illustrating an example configuration of a cellular communication system according to one embodiment. FIG. 2 is a diagram illustrating the relationship between an IAB node, parent nodes, and child nodes. FIG. 3 is a diagram illustrating an example configuration of a gNB (base station) according to one embodiment. FIG. 4 is a diagram illustrating an example configuration of an IAB node (relay node) according to one embodiment. FIG. 5 is a diagram illustrating an example configuration of a UE (user equipment) according to one embodiment. FIG. 6 is a diagram illustrating an example protocol stack related to IAB-MT RRC connection and NAS connection. FIG. 7 is a diagram illustrating an example protocol stack related to the F1-U protocol. FIG. 8 is a diagram illustrating an example protocol stack related to the F1-C protocol. FIG. 9 is a diagram illustrating an example operation according to the first embodiment. FIGS. 10(A) and 10(B) are diagrams illustrating an example operation according to the first embodiment. FIG. 11 is a diagram illustrating an example operation according to the second embodiment. FIG. 12 is a diagram illustrating scenarios and subcases of UE cell reselection. FIG. 13 is a diagram illustrating RACH-less handover configuration within MobilityControlInfo using applicable Timing Advance (TA) and uplink grant information.

[0007] A cellular communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0008] [First embodiment]

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

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

[0011] 1, the cellular communication system 1 includes a 5G core network (5GC) 10, user equipment (UE) 100, base station devices (hereinafter sometimes referred to as "base stations") 200-1 and 200-2, and IAB nodes 300-1 and 300-2. The base station 200 may be referred to as a gNB.

[0012] In the following, we will mainly describe an example in which base station 200 is an NR base station, but base station 200 may also be an LTE base station (i.e., eNB).

[0013] In the following, base stations 200-1 and 200-2 may be referred to as gNB 200 (or base station 200), and IAB nodes 300-1 and 300-2 may be referred to as IAB node 300.

[0014] The 5GC 10 has an Access and Mobility Management Function (AMF) 11 and a User Plane Function (UPF) 12. The AMF 11 is a device that performs various mobility controls for the UE 100. The AMF 11 manages information about the area in which the UE 100 is located by communicating with the UE 100 using Non-Access Stratum (NAS) signaling. The UPF 12 is a device that performs transfer control of user data, etc.

[0015] Each gNB 200 is a fixed wireless communication node and manages one or more cells. A cell is used as a term indicating the smallest unit of a wireless communication area. A cell may also be used as a term indicating a function or resource for performing wireless communication with a UE 100. One cell belongs to one carrier frequency. Hereinafter, there may be cases where a cell and a base station are used interchangeably.

[0016] Each gNB 200 is interconnected with the 5GC 10 via an interface called an NG interface. In FIG. 1, two gNBs 200-1 and 200-2 connected to the 5GC 10 are illustrated.

[0017] Each gNB 200 may be divided into a central unit (CU) and a distributed unit (DU). The CU and DU are connected to each other via an interface called an F1 interface. The F1 protocol is a communication protocol between the CU and DU, and includes the F1-C protocol, which is a control plane protocol, and the F1-U protocol, which is a user plane protocol.

[0018] The cellular communication system 1 supports IAB, which enables wireless relay of NR access using NR for backhaul. The donor gNB 200-1 (or donor node, hereinafter sometimes referred to as the "donor node") is the terminal node of the NR backhaul on the network side and is a donor base station with additional functions that support IAB. The backhaul can be multi-hopped via multiple hops (i.e., multiple IAB nodes 300).

[0019] FIG. 1 shows an example in which IAB node 300-1 wirelessly connects with donor node 200-1, IAB node 300-2 wirelessly connects with IAB node 300-1, and the F1 protocol is transmitted over two backhaul hops.

[0020] The UE 100 is a mobile wireless communication device that performs wireless communication with a cell. The UE 100 may be any device that performs wireless communication with the gNB 200 or the IAB node 300. For example, the UE 100 is a mobile phone terminal and / or a tablet terminal, a laptop PC, a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle, or an aircraft or a device provided in an aircraft. The UE 100 wirelessly connects to the IAB node 300 or the gNB 200 via an access link. FIG. 1 shows an example in which the UE 100 is wirelessly connected to the IAB node 300-2. The UE 100 indirectly communicates with the donor node 200-1 via the IAB node 300-2 and the IAB node 300-1.

[0021] FIG. 2 is a diagram showing an example of the relationship between the IAB node 300, parent nodes, and child nodes.

[0022] As shown in FIG. 2, each IAB node 300 has an IAB-DU corresponding to a base station function unit and an IAB-MT (Mobile Termination) corresponding to a user equipment function unit.

[0023] An adjacent node (i.e., an upper node) on the NR Uu radio interface of the IAB-MT is called a parent node. The parent node is the parent IAB node or the DU of the donor node 200. The radio link between the IAB-MT and the parent node is called a backhaul link (BH link). FIG. 2 shows an example in which the parent nodes of the IAB node 300 are IAB nodes 300-P1 and 300-P2. The direction toward the parent node is called upstream. From the perspective of the UE 100, the upper node of the UE 100 may correspond to the parent node.

[0024] Adjacent nodes (i.e., lower nodes) on the NR access interface of the IAB-DU are called child nodes. The IAB-DU manages the cell, similar to the gNB 200. The IAB-DU terminates the NR Uu radio interface to the UE 100 and lower IAB nodes. The IAB-DU supports the F1 protocol to the CU of the donor node 200-1. In FIG. 2, an example is shown in which the child nodes of the IAB node 300 are IAB nodes 300-C1 to 300-C3, but the child nodes of the IAB node 300 may also include the UE 100. The direction toward the child nodes is called downstream.

[0025] Furthermore, all IAB nodes 300 connected to the donor node 200 via one or more hops form a directed acyclic graph (DAG) topology (hereinafter sometimes referred to as "topology") with the donor node 200 as the root. In this topology, as shown in FIG. 2, adjacent nodes on the IAB-DU interface are child nodes, and adjacent nodes on the IAB-MT interface are parent nodes. The donor node 200 centralizes, for example, resource, topology, and route management of the IAB topology. The donor node 200 is a gNB that provides network access to the UE 100 via a network of backhaul links and access links.

[0026] (Configuration of base station) Next, the configuration of the gNB 200, which is a base station according to the embodiment, will be described. Fig. 3 is a diagram showing an example configuration of the gNB 200. As shown in Fig. 3, the gNB 200 has a wireless communication unit 210, a network communication unit 220, and a control unit 230.

[0027] The wireless communication unit 210 performs wireless communication with the UE 100 and wireless communication with the IAB node 300. The wireless communication unit 210 has a receiving unit 211 and a transmitting unit 212. The receiving unit 211 performs various receptions under the control of the control unit 230. The receiving unit 211 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 230. The transmitting unit 212 performs various transmissions under the control of the control unit 230. The transmitting unit 212 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 230 into a wireless signal, and transmits the signal from the antenna.

[0028] The network communication unit 220 performs wired communication (or wireless communication) with the 5GC10 and wired communication (or wireless communication) with other adjacent gNBs 200. The network communication unit 220 has a receiving unit 221 and a transmitting unit 222. The receiving unit 221 performs various receptions under the control of the control unit 230. The receiving unit 221 receives a signal from the outside and outputs the received signal to the control unit 230. The transmitting unit 222 performs various transmissions under the control of the control unit 230. The transmitting unit 222 transmits the transmission signal output by the control unit 230 to the outside.

[0029] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor performs processing of each layer, which will be described later. Note that the control unit 230 may perform each process or operation in the gNB 200 in each of the embodiments shown below.

[0030] (Configuration of Relay Node) Next, a configuration of an IAB node 300, which is a relay node (or relay node device; hereinafter, may be referred to as a "relay node") according to an embodiment, will be described. FIG. 4 is a diagram showing an example configuration of the IAB node 300. As shown in FIG. 4, the IAB node 300 has a wireless communication unit 310 and a control unit 320. The IAB node 300 may have multiple wireless communication units 310.

[0031] The wireless communication unit 310 performs wireless communication (BH link) with the gNB 200 and wireless communication (access link) with the UE 100. The wireless communication unit 310 for BH link communication and the wireless communication unit 310 for access link communication may be provided separately.

[0032] The wireless communication unit 310 has a receiving unit 311 and a transmitting unit 312. The receiving unit 311 performs various types of reception under the control of the control unit 320. The receiving unit 311 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 320. The transmitting unit 312 performs various types of transmission under the control of the control unit 320. The transmitting unit 312 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 320 into a wireless signal, and transmits the signal from the antenna.

[0033] The control unit 320 performs various controls in the IAB node 300. The control unit 320 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used 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. The processor performs processing of each layer, which will be described later. Note that the control unit 320 may perform each process or operation in the IAB node 300 in each of the embodiments described below.

[0034] (Configuration of User Device) Next, a configuration of the UE 100, which is a user device according to the embodiment, will be described. Fig. 5 is a diagram showing an example configuration of the UE 100. As shown in Fig. 5, the UE 100 includes a radio communication unit 110 and a control unit 120.

[0035] The wireless communication unit 110 performs wireless communication in an access link, i.e., wireless communication with the gNB 200 and wireless communication with the IAB node 300. The wireless communication unit 110 may also perform wireless communication in a side link, i.e., wireless communication with other UEs 100. The wireless communication unit 110 has a receiving unit 111 and a transmitting unit 112. The receiving unit 111 performs various receptions under the control of the control unit 120. The receiving unit 111 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 120. The transmitting unit 112 performs various transmissions under the control of the control unit 120. The transmitting unit 112 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 120 into a wireless signal, and transmits the signal from the antenna.

[0036] The control unit 120 performs various controls in the UE 100. The control unit 120 includes at least one memory and at least one processor electrically connected to the memory. The memory stores 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, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor performs processing of each layer, which will be described later. Note that the control unit 120 may be configured to perform each process in the UE 100 in each of the embodiments described below.

[0037] (Protocol Stack Configuration) Next, a description will be given of the configuration of a protocol stack according to the embodiment. Fig. 6 is a diagram showing an example of a protocol stack related to an IAB-MT RRC connection and a NAS connection.

[0038] As shown in FIG. 6, the IAB-MT of IAB node 300-2 has a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) layer, and a non-access stratum (NAS) layer.

[0039] 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 IAB-MT of IAB node 300-2 and the PHY layer of the IAB-DU of IAB node 300-1 via a physical channel.

[0040] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted via transport channels between the MAC layer of the IAB-MT of IAB node 300-2 and the MAC layer of the IAB-DU of IAB node 300-1. The MAC layer of the IAB-DU includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the allocated resource blocks.

[0041] 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 IAB-MT of IAB node 300-2 and the RLC layer of the IAB-DU of IAB node 300-1 via logical channels.

[0042] The PDCP layer performs header compression / decompression, and encryption / decryption. Data and control information are transmitted between the PDCP layer of the IAB-MT of the IAB node 300-2 and the PDCP layer of the donor node 200 via a radio bearer.

[0043] The RRC layer controls logical channels, transport channels, and physical channels in response to the establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the IAB-MT of the IAB node 300-2 and the RRC layer of the donor node 200. When there is an RRC connection with the donor node 200, the IAB-MT is in an RRC connected state. When there is no RRC connection with the donor node 200, the IAB-MT is in an RRC idle state.

[0044] 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 IAB-MT of the IAB node 300-2 and the AMF 11.

[0045] Figure 7 shows a protocol stack for the F1-U protocol. Figure 8 shows a protocol stack for the F1-C protocol. Here, an example is shown in which the donor node 200 is divided into a CU and a DU.

[0046] As shown in Figure 7, the IAB-MT of IAB node 300-2, the IAB-DU of IAB node 300-1, the IAB-MT of IAB node 300-1, and the DU of donor node 200 each have a BAP (Backhaul Adaptation Protocol) layer above the RLC layer. The BAP layer is a layer that performs routing processing and bearer mapping / demapping processing. In the backhaul, the IP layer is transmitted via the BAP layer, enabling routing over multiple hops.

[0047] In each backhaul link, PDUs (Protocol Data Units) of the BAP layer are transmitted by a backhaul RLC channel (BH NR RLC channel). By configuring multiple backhaul RLC channels in each BH link, traffic prioritization and QoS (Quality of Service) control are possible. The association between BAP PDUs and backhaul RLC channels is performed by the BAP layer of each IAB node 300 and the BAP layer of the donor node 200.

[0048] As shown in FIG. 8, the protocol stack of the F1-C protocol has an F1AP layer and an SCTP layer instead of the GTP-U layer and UDP layer shown in FIG.

[0049] In the following, the processing or operations performed by the IAB-DU and IAB-MT of the IAB may be simply described as the processing or operations of the "IAB." For example, the transmission of a BAP layer message from the IAB-DU of IAB node 300-1 to the IAB-MT of IAB node 300-2 will be described as the IAB node 300-1 sending the message to IAB node 300-2. In addition, the processing or operations of the DU or CU of the donor node 200 may also be simply described as the processing or operations of the "donor node."

[0050] Also, the upstream direction and the uplink (UL) direction may be used interchangeably, and the downstream direction and the downlink (DL) direction may be used interchangeably.

[0051] (Mobile IAB Node) Currently, 3GPP has begun discussions toward the introduction of mobile IAB nodes. A mobile IAB node is, for example, an IAB node that is moving. A mobile IAB node may be an IAB node that is capable of moving. Alternatively, a mobile IAB node may be an IAB node that is currently stationary but is certain to move in the future (or is expected to move in the future).

[0052] The mobile IAB node enables, for example, a UE 100 under the mobile IAB node to receive services from the mobile IAB node while moving in accordance with the movement of the mobile IAB node. For example, a case is envisioned in which a user (or UE 100) on a vehicle receives services via a mobile IAB node installed on the vehicle.

[0053] On the other hand, in contrast to mobile IAB nodes, there are also IAB nodes that do not move. Such IAB nodes are sometimes referred to as intermediate IAB nodes. An intermediate IAB node is, for example, an IAB node that does not move. Alternatively, the intermediate IAB node may be a stationary IAB node. Alternatively, the intermediate IAB node may be an IAB node that remains stationary (or does not move) and remains installed at its installation location. Alternatively, the intermediate IAB node may be a stationary IAB node that does not move. The intermediate IAB node may also be a fixed IAB node.

[0054] A mobile IAB node can also be connected to an intermediate IAB node. Also, a mobile IAB node can be connected to a donor node 200. A mobile IAB node can also change its connection destination due to movement (migration or handover). The connection source may be an intermediate IAB node. The connection source may be the donor node 200. Also, the connection destination may be an intermediate IAB node. The connection destination may be the donor node 200.

[0055] In the following, the terms "migration" of a mobile IAB node and "handover" of a mobile IAB node may be used interchangeably.

[0056] In the following description, the mobile IAB node may be referred to as a "mobile IAB node." The mobile IAB node may also be referred to as a "migrating IAB node." In either case, the mobile IAB node may be referred to as a mobile IAB node.

[0057] (Cell Reselection Procedure) Next, a cell reselection procedure according to the first embodiment will be described.

[0058] A UE 100 in an RRC idle state or an RRC inactive state performs a cell reselection procedure to transition from a current serving cell to a neighboring cell as it moves. Specifically, the UE 100 identifies a neighboring cell on which it should camp by the cell reselection procedure and reselects the identified neighboring cell. When the frequency (carrier frequency) of the current serving cell and the neighboring cell is the same, this is called intra-frequency, and when the frequency (carrier frequency) of the current serving cell and the neighboring cell is different, this is called inter-frequency. The current serving cell and the neighboring cell may be managed by the same gNB 200. The current serving cell and the neighboring cell may be managed by different gNBs 200.

[0059] Cell reselection procedures include intra-frequency cell reselection procedures and inter-frequency cell reselection procedures.

[0060] In the intra-frequency cell reselection procedure, cell reselection is performed based on the cell ranking. In the intra-frequency cell reselection procedure, for example, the following processing is performed.

[0061] First, the UE 100 performs a measurement process to measure radio quality for each of the serving cell and the neighboring cell. Specifically, the UE 100 measures RSRP and RSRQ of CD-SSB (Cell Defining-Synchronization Signal and PBCH block) for each of the serving cell and the neighboring cell.

[0062] Second, the UE 100 calculates a ranking criterion (Rs) for the serving cell and a ranking criterion (Rn) for the neighboring cell for all cells that satisfy the cell selection criterion S. Rs and Rn are calculated using the following formulas, respectively.

[0063] Rs = Q ｍｅａｓ，ｓ +Q ｈｙｓｔ -Qoffset ｔｅｍｐ ...(1) Rn=Q ｍｅａｓ，ｎ -Qoffset-Qoffset ｔｅｍｐ ...(2) In formula (1), Q ｍｅａｓ，ｓ represents the reference signal received power (RSRP) (measurement value) for the serving cell. ｍｅａｓ，ｎ represents the RSRP (measured value) for the neighboring cell. Qoffset is an offset value for adjusting the RSRP. ｔｅｍｐ is a temporary offset value.

[0064] The UE 100 basically reselects the cell with the highest rank from among the two ranking criteria Rs and Rn.

[0065] Here, as shown in equation (2), an offset value (Qoffset) is used for Rn. The Qoffset is provided from the gNB 200 to the UE 100 using broadcast signaling (for example, a system information block (SIB)). The Qoffset can be adjusted for each frequency or each cell. By adjusting the Qoffset, the network side can control the ease of reselection between the serving cell and the neighboring cell.

[0066] The cell selection criterion S is a criterion for selecting a cell whose RSRP exceeds the minimum required RSRP level and whose RSRQ exceeds the minimum required RSRQ level.

[0067] On the other hand, in the inter-frequency cell reselection procedure, cell reselection is performed based on absolute frequency priority. The frequency priority is provided from the gNB 200 to the UE 100 by broadcast signaling (e.g., a system information block) or dedicated signaling (e.g., an RRC Release message). In the inter-frequency cell reselection procedure, for example, the following processing is performed.

[0068] First, the UE 100 performs a measurement process (measurement) to measure the radio quality of each of the serving cell and the neighboring cell. Specifically, the UE 100 always measures the radio quality of a frequency having a higher priority than the priority of the frequency of the current serving cell. Furthermore, for a frequency having a priority equal to or lower than the priority of the frequency of the current serving cell, the UE 100 measures the radio quality of the frequency having the same priority or a lower priority when the radio quality of the current serving cell falls below a predetermined quality.

[0069] Second, the UE 100 performs a cell reselection process to reselect a cell on which the UE 100 camps based on the measurement result. Specifically, when the frequency priority of a neighboring cell is higher than the priority of the current serving cell and the neighboring cell satisfies a predetermined quality standard (i.e., a minimum required quality standard) for a predetermined period, the UE 100 may perform cell reselection to the neighboring cell. When the frequency priority of the neighboring cell is the same as the priority of the current serving cell, the UE 100 may rank the radio qualities of the neighboring cells and perform cell reselection to a neighboring cell having a higher rank than the rank of the current serving cell for a predetermined period. When the frequency priority of the neighboring cell is lower than the priority of the current serving cell and the radio quality of the current serving cell is lower than a certain threshold and the radio quality of the neighboring cell is higher than another threshold, the UE 100 may perform cell reselection to the neighboring cell.

[0070] Although the above example describes an example in which the UE 100 performs the cell reselection procedure, it is also possible for the IAB-MT of the IAB node 300 to perform the cell reselection procedure.

[0071] (Communication Control Method According to First Embodiment) Next, a description will be given of a communication control method according to the first embodiment. In the first embodiment, an intra-frequency cell reselection procedure in a mobile IAB node will be described.

[0072] A mobile IAB node can broadcast mobile IAB cell type information (mobile-IAB cell type indication) (or mobile relay node cell type information) indicating that the mobile IAB node itself is a mobile IAB node. The mobile IAB cell type information makes it possible to assist the movement of a UE 100 in, for example, an RRC idle state or an RRC inactive state. The mobile IAB cell type information is, for example, 1-bit information. Furthermore, together with (or instead of) the mobile IAB cell type information, movement speed information indicating the movement speed of the mobile IAB node may be broadcast. In this way, by the mobile IAB node broadcasting the mobile IAB cell type information (and / or movement speed information), the UE 100 receiving the information can recognize that the cell that broadcast the information is a cell of the mobile IAB node.

[0073] On the other hand, in the intra-frequency cell reselection procedure, as described above, reselection is performed based on ranking using equations (1) and (2). Here, assume that the intra-frequency cell reselection procedure is applied to a mobile IAB node. Even in such a case, the network side can control the ease of reselection to the mobile IAB node's cell (hereinafter, this cell may be referred to as a "mobile IAB cell") by adjusting, for example, the Qoffset in equation (2).

[0074] However, there is only one type of Qoffset. In a non-mobile IAB node, when a mobile IAB node enters the non-mobile IAB node's cell (hereinafter, the cell may be referred to as a "non-mobile IAB cell." A "non-mobile IAB cell" may include a cell served by a fixed (stationary) IAB node. A "non-mobile IAB cell" may also include a cell served by a conventional base station (such as a macro cell), the Qoffset may be changed for the mobile IAB node, and the SIB may also be updated based on the change. Furthermore, in a non-mobile IAB node, when a mobile IAB node leaves the non-mobile IA node's cell, the Qoffset may be restored and the SIB may be updated again based on the change. In this way, a non-mobile IAB node may update the SIB every time a mobile IAB node enters or leaves the non-mobile IAB cell. Furthermore, even in a mobile IAB node, there are cases where the Qoffset for the subordinate UE 100 is adjusted and the SIB broadcast by the mobile IAB node is updated every time the mobile IAB node moves into or moves out of the non-mobile IAB cell.

[0075] Therefore, the first embodiment aims to suppress the frequency of updating the SIB.

[0076] Therefore, in the first embodiment, first, a relay node (e.g., IAB node 300) broadcasts a mobile relay node offset value (e.g., mobile IAB node offset value), and second, a user equipment (e.g., UE 100) performs an intra-frequency cell reselection procedure using the mobile relay node offset value.

[0077] In this way, the IAB node 300 broadcasts the offset value for the mobile IAB node, and the UE 100 executes the intra-frequency cell reselection procedure using the offset value for the mobile IAB node. Therefore, by using the offset value for the mobile IAB node, the network side does not need to adjust the Qoffset for the mobile IAB node. Therefore, it is possible to reduce the frequency of SIB updates due to the Qoffset adjustment.

[0078] Note that the non-mobile IAB node is, for example, a node other than a mobile IAB node. The non-mobile IAB node may be an intermediate IAB node. The non-mobile IAB node may be a donor node 200 (or a gNB 200).

[0079] (Example of Operation According to First Embodiment) Next, an example of operation according to the first embodiment will be described.

[0080] FIG. 9 is a diagram illustrating an example of operation according to the first embodiment.

[0081] 9, in step S10, the mobile IAB cell 300-M broadcasts mobile IAB cell type information, but the non-mobile IAB cell 300-N does not broadcast mobile IAB cell type information.

[0082] In step S11, the UE 100 transitions to an RRC idle state or an RRC inactive state.

[0083] In step S12, the UE 100 receives mobile IAB cell type information (and / or movement speed information) broadcast from the mobile IAB cell 300-M. The UE 100 may receive the mobile IAB cell type information when starting an intra-frequency cell reselection procedure and performing measurements on the serving cell and neighboring cells. The UE 100 can determine whether the serving cell and neighboring cells are mobile IAB nodes depending on whether the UE 100 has received the IAB cell type information.

[0084] In step S13, the mobile IAB cell 300-M broadcasts the mobile IAB node offset value. The mobile IAB node offset value is, for example, an offset value for adjusting the RSRP (measured value) used in the ranking criterion R (Rs and Rn).

[0085] First, the mobile IAB cell 300-M may broadcast the offset value for the mobile IAB node using the SIB, or alternatively, the mobile IAB cell 300-M may transmit the offset value for the mobile IAB node using dedicated signaling (e.g., an RRC release message).

[0086] Second, the mobile IAB cell 300-M may broadcast a mobile IAB node offset value such that the RSRP of the mobile IAB cell 300-M is higher than the RSRP of the non-mobile IAB cell 300-N. Such an offset value enables the network to allow the UE 100 camped on the mobile IAB cell 300-M to continue camping on the mobile IAB cell 300-M. Alternatively, the mobile IAB cell 300-M may broadcast a mobile IAB node offset value such that the RSRP of the mobile IAB cell 300-M is lower than the RSRP of the non-mobile IAB cell 300-N.

[0087] In step S14, the non-mobile IAB cell 300-N broadcasts the offset value for the mobile IAB node.

[0088] First, the non-mobile IAB cell 300-N may also broadcast the offset value in the SIB, as in the mobile IAB cell 300-M, or may transmit the offset by dedicated signaling (for example, an RRC release message).

[0089] Second, the non-mobile IAB cell 300-N may broadcast a mobile IAB node offset value such that the RSRP of the mobile IAB cell 300-M (neighbor cell) is lower than the RSRP of the non-mobile IAB cell 300-N. Alternatively, the non-mobile IAB cell 300-N may broadcast a mobile IAB node offset value such that the RSRP of the mobile IAB cell 300-M (neighbor cell) is higher than that of the non-mobile IAB cell 300-N.

[0090] As shown in steps S13 and S14, different offset values ​​may be broadcast for the mobile IAB node depending on whether the cell of the IAB node 300 is a cell of the mobile IAB node (i.e., a mobile IAB cell 300-M) or a cell other than a mobile IAB node (i.e., a non-mobile IAB cell 300-N).

[0091] In step S15, the UE 100 executes an intra-frequency cell reselection procedure. If the UE 100 has started execution of the procedure in step S12, the UE 100 may calculate ranking criteria R (Rs and Rn) in the procedure in step S15. The UE 100 uses the offset value for the mobile IAB node, for example, as follows.

[0092] First, the operation when the UE 100 is camped on the non-moving IAB cell 300-N (i.e., the moving IAB cell 300-M is a neighbor cell) is shown in Fig. 10A.

[0093] That is, when the UE 100 is camped on the non-moving IAB cell 300-N, the ranking criterion Rn for the neighboring cells is set to the RSRP measurement value (Q ｍｅａｓ，ｎ ) by subtracting the offset value for the mobile IAB node (or by adding the offset value for the mobile IAB node that is a negative offset value).

[0094] This allows the network side to perform control so that, for example, it becomes difficult for the UE 100 camped on the non-moving IAB cell 300-N to reselect to the moving IAB cell 300-M.

[0095] This operation may be performed when the mobility state of the UE 100 is a slow-moving state (“Normal-mobility state” or “Medium-mobility state”). This is because the UE 100 is camped on the non-moving IAB cell 300-N, and therefore is more likely to be in a slow-moving state than when camped on the moving IAB cell 300-M.

[0096] In this way, when the UE 100 is camped on the non-mobile IAB cell 300-N, the UE 100 subtracts the offset value for the mobile IAB node from the RSRP for the mobile IAB cell 300-M.

[0097] Second, the operation is performed when the UE 100 is camped on the mobile IAB cell 300-M (i.e., the mobile IAB cell 300-M is the serving cell). Fig. 10B shows an example of the operation in this case.

[0098] That is, when the UE 100 is camped on the mobile IAB cell 300-M, the ranking criterion Rs for the serving cell is the RSRP measurement value (Q ｍｅａｓ，ｓ ) (or, if the offset value for the mobile IAB node is a negative offset value, the offset value for the mobile IAB node is subtracted).

[0099] This allows the network side to perform control so that the UE 100 camped on the mobile IAB cell 300-M continues to reselect the mobile IAB cell 300-M, for example.

[0100] In this way, when the UE 100 is camped on the mobile IAB cell 300-M, the UE 100 adds the mobile IAB node offset value to the RSRP for the mobile IAB cell 300-M.

[0101] Note that, when the UE 100 is camped on the mobile IAB cell 300-M, the UE 100 may perform this operation when the neighboring cell is not the mobile IAB cell 300-M (i.e., when the neighboring cell is the non-mobile IAB cell 300-N). On the other hand, when the UE 100 is camped on the mobile IAB cell 300-M, if the neighboring cell is the mobile IAB cell 300-M, the UE 100 may perform the intra-frequency cell reselection procedure (i.e., calculate the ranking criterion R) without using the mobile IAB node offset value. For example, considering a scenario in which the intra-frequency cell reselection procedure is performed between multiple mobile IAB cells 300-M, not using the mobile IAB node offset value between the mobile IAB cells 300-M makes it easier for the UE 100 to reselect the mobile IAB cell 300-M.

[0102] In addition, when the UE 100 is camped on the mobile IAB cell 300-M, the RSRP measurement value (Q ｍｅａｓ，ｓ Instead of adding an offset value for the mobile IAB node to the ranking criteria Rn for the neighboring cells, the RSRP measurement value (Q ｍｅａｓ，ｎ ) by subtracting the offset value for the mobile IAB node (or by adding the offset value if the offset value for the mobile IAB node is a negative offset value).

[0103] Furthermore, the above-described operation when the UE 100 is camped on the moving IAB cell 300-M may be performed when the UE 100 is in a high-mobility state. This is because the UE 100 is on-board with the moving IAB cell 300-M and is therefore more likely to be in a high-mobility state than when the UE 100 is camped on a non-moving IAB cell 300-N.

[0104] The gNB 200 may configure the UE 100 as to how to apply the offset for the mobile IAB node. In addition to the above-described example, the gNB 200 may also configure the following. That is, in the case of a normal mobility state ("Normal-mobility state"), the gNB 200 performs RSRP measurement (Q ｍｅａｓ，ｎ ) from the mobile IAB node offset value (or, if the mobile IAB node offset value is a negative offset value, add the offset value). In addition, in the case of a medium-mobility state ("Medium-mobility state") or a high-mobility state ("High-mobility state"), the gNB 200 may set the RSRP measurement value (Q ｍｅａｓ，ｓ ) may be set to add an offset value for the mobile IAB node. Instead of this addition, the gNB 200 may use the RSRP measurement value (Q ｍｅａｓ，ｎ) by subtracting the offset value for the mobile IAB node (or by adding the offset value if the offset value for the mobile IAB node is a negative offset value).

[0105] (Another Operation Example 1 According to the First Embodiment) In the first embodiment, a case has been described in which the offset value for the mobile IAB node is used in the ranking criteria R (Rs and Rs) of the intra-frequency cell reselection procedure, but this is not limiting.

[0106] First, the mobile IAB node offset value may be used in the cell selection criterion S in the cell selection procedure. As described above, in the cell selection criterion S, the RSRP is compared with the minimum required RSRP level. The mobile IAB node offset value may be applied to the RSRP. As in the first embodiment, the cell selection criterion S may be determined by adding or subtracting the mobile IAB node offset value depending on whether the cell to be measured is the mobile IAB cell 300-M or the non-mobile IAB cell 300-N.

[0107] Second, the mobile IAB node offset value may be used in measurement processing for inter-frequency cell reselection. For example, when comparing a measured RSRP with a threshold, the mobile IAB node offset value may be applied to the RSRP. As in the first embodiment, the mobile IAB node offset value may be added to or subtracted from the RSRP depending on whether the cell to be measured is the mobile IAB cell 300-M or the non-mobile IAB cell 300-N.

[0108] (Another Operation Example 2 According to First Embodiment) In the first embodiment, the addition and subtraction of the offset value for the mobile IAB node to the RSRP may be reversed. For example, when the UE 100 is camped on the non-mobile IAB cell 300-N, the UE 100 calculates the RSRP measurement value (Q ｍｅａｓ，ｎ) may be added with an offset value for the mobile IAB node (if the offset value for the mobile IAB node is a negative offset value, the offset value may be subtracted). Also, for example, when the UE 100 is camped on the mobile IAB cell 300-M, the RSRP measurement value for the serving cell (Q ｍｅａｓ，ｓ ) by subtracting the offset value for the mobile IAB node (or by adding the offset value if the offset value for the mobile IAB node is a negative offset value).

[0109] Second Embodiment Next, a second embodiment will be described, in which an inter-frequency cell reselection procedure will be described.

[0110] The inter-frequency cell reselection procedure in the mobile IAB cell 300-M can use the existing procedure using frequency priority.

[0111] That is, the mobile IAB cell 300-M sets the frequency priority of the frequency used in its own mobile IAB cell 300-M higher than the frequency priority of the frequency used in the non-mobile IAB cell 300-N. By broadcasting this frequency priority, the mobile IAB cell 300-M makes it difficult for the UE 100 camped on the mobile IAB cell 300-M to reselect the non-mobile IAB cell 300-N. On the other hand, the non-mobile IAB cell 300-N sets the frequency priority of the frequency used in the mobile IAB cell 300-M lower than the frequency priority of the frequency used by itself. By broadcasting this frequency priority, the non-mobile IAB cell 300-N makes it easier for the UE 100 camped on the non-mobile IAB cell 300-N to reselect the mobile IAB cell 300-M.

[0112] On the other hand, 3GPP specifies a high speed dedicated network (HSDN) (for example, 3GPP TS 38.304 V17.2.0 (2022-09)). In the HSDN, a cell called an HSDN cell (high speed dedicated network cell) exists. The HSDN cell broadcasts HSDN cell information (hsdn-cell) indicating that the HSDN cell is an HSDN. A UE 100 in a high-mobility state can regard the HSDN cell as the highest priority cell. On the other hand, a UE 100 that is not in a high-mobility state can regard the HSDN cell as the lowest priority cell. For example, a UE 100 traveling on a high-speed train can more easily reselect an HSDN cell installed along the tracks in preference to other cells. Therefore, the HSDN can adequately support communications with UEs moving at high speed.

[0113] Assume that HSDN is applied to the mobile IAB cell 300-M. In this case, the mobile IAB cell 300-M broadcasts HSDN cell information (hsdn-cell). When the UE 100 receives the HSDN cell information and is in a high-speed moving state, the UE 100 can regard the mobile IAB cell as the highest-priority cell. On the other hand, when the UE 100 receives the HSDN cell information and is in a low-speed moving state, the UE 100 can regard the mobile IAB cell as the lowest-priority cell.

[0114] However, if UE 100 considers the moving IAB cell 300-M to be the lowest priority cell even if UE 100 is moving at a low speed, UE 100 may not be able to reselect the moving IAB cell 300-M in the inter-frequency cell reselection procedure.

[0115] Therefore, in the second embodiment, first, a user equipment (e.g., UE 100) receives from a cell High Speed ​​Dedicated Network (HSDN) cell information indicating that the cell is an HSDN cell and mobile relay node cell type information (e.g., mobile IAB cell type information) indicating that the cell is a cell of the mobile relay node, and second, when in a low-speed moving state, the user equipment performs an inter-frequency cell reselection procedure without considering the cell as the lowest priority.

[0116] As a result, the UE 100 that has received the UHSDN cell information and the mobile IAB cell type information does not regard the mobile IAB cell as the lowest priority cell even when moving at a low speed. Therefore, the UE 100 can appropriately reselect the mobile IAB cell in the inter-frequency cell reselection procedure.

[0117] (Example of Operation According to Second Embodiment) Next, an example of operation according to the second embodiment will be described.

[0118] FIG. 11 is a diagram illustrating an example of operation according to the second embodiment.

[0119] 11, in step S20, the mobile IAB cell 300-M broadcasts HSDN cell information and mobile IAB cell type information. The mobile IAB cell 300-M may broadcast using the SIB. The non-mobile IAB cell 300-N does not broadcast at least the mobile IAB cell type information. The non-mobile IAB cell 300-N may broadcast the HSDN cell information.

[0120] In step S21, the UE 100 transitions to an RRC idle state or an RRC inactive state.

[0121] In step S22, the UE 100 receives the HSDN cell information and the mobile IAB cell type information (and / or the movement speed information) broadcast from the moving IAB cell 300-M. The UE 100 may start an inter-frequency cell reselection procedure and receive the HSDN cell information and the mobile IAB cell type information during a measurement process. The UE 100 can determine whether each cell is the moving IAB cell 300-M or the non-moving IAB cell 300-N depending on whether the mobile IAB cell type information is received.

[0122] In step S23, the UE 100 that has received the HSDN cell information and the mobile IAB cell type information performs a predetermined process. Specifically, the predetermined process is as follows.

[0123] That is, in the case of a high-mobility state, the UE 100 regards the cell that has transmitted the HSDN cell information and the mobile IAB cell type information as the highest-priority cell. On the other hand, in the case of a low-mobility state ("normal-mobility state" or "medium-mobility state"), the UE 100 does not regard the cell that has transmitted the HSDN cell information and the mobile IAB cell type information as the lowest-priority cell. In this case, the UE 100 performs an inter-frequency cell reselection procedure using the frequency priority provided from the cell (e.g., by an SIB or an RRC release message).

[0124] Note that the UE 100 may determine the moving state using a speed sensor, a GNSS (Global Navigation Satellite System) receiver, or the like.

[0125] [Other Embodiments] The above-described operational flows are not limited to being implemented independently, but can be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0126] In the above-described embodiments and examples, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0127] Also, the term "network node" primarily refers to a base station, but may also refer to a device in the core network or part of a base station (CU, DU, or RU).

[0128] A program that causes a computer to execute each process performed by the UE 100 or the gNB 200 may be provided. The program may be recorded on a computer-readable medium. Using a 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, but may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0129] In addition, circuits that perform each process performed by UE100 or gNB200 may be integrated, and at least a portion of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0130] As used in this disclosure, the terms "based on" and "depending on / in response to" 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.

[0131] 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 within the scope of the gist. Furthermore, the embodiments, operation examples, and processes can be appropriately combined within the scope of not being inconsistent.

[0132] This application claims priority to U.S. Provisional Application No. 63 / 421,712 (filed November 2, 2022), the entire contents of which are incorporated herein by reference.

[0133] (Supplementary Note 1) (Supplementary Note 1) A communication control method used in a cellular communication system, comprising: a step in which a relay node broadcasts an offset value for a mobile relay node; and a step in which a user equipment performs an intra-frequency cell reselection procedure using the offset value for the mobile relay node.

[0134] (Supplementary Note 2) The communication control method according to Supplementary Note 1, wherein the step of reporting includes a step of reporting a different offset value for the mobile relay node depending on whether the relay node is a mobile relay node or a relay node other than the mobile relay node.

[0135] (Supplementary Note 3) The communication control method according to Supplementary Note 1 or Supplementary Note 2, wherein the executing step includes a step in which the user equipment changes a method of applying the offset value for the mobile relay node depending on whether the serving cell and the neighboring cell are cells of the mobile relay node.

[0136] (Supplementary Note 4) The communication control method described in any one of Supplementary Notes 1 to 3, wherein the changing step includes a step of subtracting the mobile relay node offset value from the reference signal received power for the cell of the mobile relay node when the user equipment is camped on a cell of a relay node other than the mobile relay node, and adding the mobile relay node offset value to the reference signal received power for the cell of the mobile relay node when the user equipment is camped on the cell of the mobile relay node.

[0137] (Supplementary Note 5) The communication control method according to any one of Supplementary Notes 1 to 4, further comprising a step in which, in the adding step, the user equipment subtracts the offset value for the mobile relay node from the reference signal received power for a cell of the relay node other than the mobile relay node, instead of adding the offset value for the mobile relay node.

[0138] (Supplementary Note 6) The communication control method according to any one of Supplementary Notes 1 to 5, wherein the changing step performs the intra-frequency cell reselection procedure without using the mobile relay node offset value when the user equipment is camped on a cell of the mobile relay node and the neighboring cell is also a cell of the mobile relay node.

[0139] (Supplementary Note 7) The communication control method according to any one of Supplementary Notes 1 to 6, further comprising the step of the user equipment performing a cell reselection procedure using the mobile relay node offset value.

[0140] (Supplementary Note 8) The communication control method according to any one of Supplementary Notes 1 to 7, further comprising the step of the user equipment performing an inter-frequency cell reselection procedure using the mobile relay node offset value.

[0141] (Supplementary Note 9) The communication control method according to any one of Supplementary Note 1 to Supplementary Note 8, further comprising a step of: a mobile relay node broadcasting mobile relay node cell type information indicating that the node itself is the mobile relay node.

[0142] (Supplementary Note 10) A communication control method for use in a cellular communication system, comprising: a step of receiving, by a user equipment, from a cell, High Speed ​​Dedicated Network (HSDN) cell information indicating that the cell is an HSDN cell and mobile relay node cell type information indicating that the cell is a cell of a mobile relay node; and a step of performing an inter-frequency cell reselection procedure by the user equipment when in a low-speed moving state, without regarding the cell as a lowest-priority cell.

[0143] (Supplementary Note 11) The communication control method according to any one of Supplementary Notes 1 to 10, further comprising: receiving, by the user equipment, a frequency priority of a frequency used in the cell; and the performing step includes performing, by the user equipment, the inter-frequency cell reselection procedure using the frequency priority of the cell.

[0144] (Second Supplement) Introduction The Mobile IAB WID was revised in RAN#97e with the following objectives:

[0145] The detailed objectives of WI are to: Define transition / topology adaptation procedures to enable IAB node mobility, including inter-donor transition (full transition) of the entire mobile IAB node. A mobile IAB node can be attached to a fixed (intermediate) IAB node. Optimizations specific to scenarios where a mobile IAB node connects to a fixed (intermediate) IAB node or where the mobile IAB node directly connects to an IAB donor DU are given a low priority. Mobility of dual-attached IAB nodes is given a low priority. Enhancements to mobility of IAB nodes and their served UEs, including aspects related to group mobility. There are no optimizations for targeting surrounding UEs. Note: Solutions should avoid touching on topics already under discussion for Rel-17 or that have been excluded from Rel-17, except for enhancements specific to IAB node mobility. Mitigation of interference due to IAB node mobility, including avoidance of potential reference and control signal collisions (e.g., PCI, RACH). The following principles must be respected: - Mobile IAB nodes must be able to serve legacy UEs. - Solutions providing mobile IAB optimization may require Rel-18 UE extensions, provided that such extensions are backward compatible.

[0146] One of the key challenges in Rel-18 is how to efficiently perform handover of multiple descendant UEs during the transition of a mobile IAB node. This appendix provides details of the mobility enhancements for mobile IAB.

[0147] Discussion UE Mobility Enhancements UE Handover Procedures RAN2#119bis-e has reached the following agreement regarding UE handover procedures:

[0148] If the two logical DU cells use distinct physical resources (i.e., different carriers, or orthogonal time and frequency resources of the same carrier, as supported in legacy L1), RAN2 focuses on the scenario where the UE recognizes the two logical DU cells as different physical cells (e.g., different PCIs in the case of the same carrier) during full transition.

[0149] From the QCtdoc, the following options O1, O2 and O3 are considered: 1) Message deferral by logical source IAB-DU with conditional delivery (e.g. during MT transition), 2) Conditional execution by UE based on broadcast indication, e.g. SIB indication of service time or DCI indication of MT transition (including CHO with new triggers), 3) Legacy CHO (implementation specific behavior, e.g. using source cell power down or target cell power up to trigger actual HO). RAN2 assumes that O1 and O3 above may work, and further consideration is required for the case where O2 above (e.g. new trigger) is required.

[0150] O1 is considered the baseline because it is pending delivery and works for Rel-15 UEs. O3 with its current conditional handover (CHO) works for Rel-16 and later UEs. Therefore, further consideration is needed as to whether to enhance CHO for Rel-18, for example, based on O3.

[0151] Since viable solutions already exist, such as O1 and O3, it is questionable whether enhancements are really necessary. On the other hand, it is expected that at some point in the future, Rel-18 UEs will become the majority in the network. In this case, if the existing solutions have some shortcomings, it would be useful to make some enhancements for Rel-18 and later UEs. When new solutions are discussed, one of the key points will be to avoid signaling storms caused by UE handovers, as pointed out in RAN2#119bis-e.

[0152] Proposal 1: RAN2 should discuss whether there are problems with the existing solutions for UE handover, namely, deferred delivery (O1) and CHO (O3).

[0153] In case O1, the RRC reconfiguration with synchronization is pending by the mobile IAB node and delivered to the UE once the mobile IAB-MT has completed the transition to the target donor. The timing of the transmission of the RRC reconfiguration message can be managed by the mobile IAB node. Therefore, the timing of the reception of the RRC Reconfiguration Complete message is controllable. This depends on the time for which the two cells (i.e., provided by dual DU) are maintained, but during this period there may be some DL load in the source cell and some UL load in the target cell.

[0154] In the case of O3, the RRC reconfiguration, including the conditional reconfiguration, is sent in advance by the IAB donor through the mobile IAB node, thus enabling the UE handover command to be prepared in advance and DL load to be distributed in time within the source cell. On the other hand, CHO is performed when existing events (A3 / A5) are met. Since O3 relies on the radio conditions of the source / target cells (i.e., by controlling the transmit power), in particular the source and target cells are served by physically collocated antennas.

[0155] Considering the above observations, O1 may need to maintain the source and target cells for a long time to reduce the DL / UL load. O3 may cause UL signaling storms at the target cell. Therefore, if a new solution is introduced, these problems should be resolved. That is, two cells (provided by dual DU) should be maintained for a minimum period to avoid signaling storms.

[0156] Proposal 2: Even if the source and target cells are retained for a minimum period during the transition of a mobile IAB node, if CHO is extended for Rel-18 UEs, RAN2 should agree that the solution must avoid signaling storms in the DL (source cell) and UL (target cell).

[0157] Enhancements to UE Cell Reselection RAN2#119bis-e has agreed to the following confirmations, observations and assumptions:

[0158] RAN2 recognizes that mobile IAB needs to work with legacy UEs. RAN2 recognizes that if a UE is camped / attached to a mobile IAB cell for an extended period of time, it may consider itself to be on a mobile IAB cell (i.e., the UE needs to know that this is such a cell). Time requires further consideration.

[0159] RAN2 makes the following assumptions for UEs operating in mobile IAB cells: Assumption 1: From the perspective of the network of a mobile IAB cell, the principles for setting legacy parameters (including cell (re)selection, cell reservation, and access restriction) remain unchanged compared to legacy IAB cells. Assumption 2: There is no impact of the specifications on the operation of legacy UEs. Assumption 3: The newly broadcasted information of R18 of a mobile IAB cell (if agreed) does not prohibit / control the access of legacy UEs. Assumption 4: Non-enhanced UEs (including legacy UEs that do not support enhancements and R18 UEs) ignore the newly broadcasted information of R18 of a mobile IAB cell (if agreed). RAN2 assumption: For mobile IAB cell broadcast information To support mobility in idle / inactive mode for Rel-18 UEs, one bit of mobile-IAB cell type indication (or mobile relay node cell type information) has been introduced (further study is needed on whether it allows UEs to know they are onboard). How it is used needs further study (might be implementation specific). RAN2 has not specified any changes to prevent surrounding UEs from accessing mobile IAB nodes from the perspective of mobile IAB WI, but it is considered that SA2 may be working on a Rel-18 solution that may be applicable.

[0160] Two main scenarios and several subcases for expected UE behavior are considered: Scenario A: The mobile IAB node is moving with the camped UE (e.g., the train is moving). Subcase A1: The UE (e.g., on the train) should stay on the mobile IAB node. Subcase A2: Surrounding UEs (e.g., outside the train) should not stay on the mobile IAB node. Scenario B: The mobile IAB node is stationary with the camped UE (e.g., the train is stopped at the station). Subcase B1: The UE (e.g., still on the train) should stay on the mobile IAB node. Subcase B2: The UE (e.g., getting off the train) needs to reselect a fixed cell (e.g., a macrocell). Subcase B3: Surrounding UEs (e.g., getting on the train) need to reselect a mobile IAB node. Subcase B4: Surrounding UEs (e.g., still in the station) should stay in their fixed cells.

[0161] In subcase A1, the UE moves with the mobile IAB node. Therefore, the RSRP and RSRQ from the mobile IAB node are always stable and of sufficient quality. No cell reselection procedure is triggered. To be precise, if the frequency priority of the mobile IAB node is higher than outside the cell, the UE may not be able to perform intra-frequency or inter-frequency measurements. For example, the mobile IAB node broadcasts its frequency priority as "7" or broadcasts its cell as an HSDN cell.

[0162] A train can be considered to have multiple cars, with a mobile IAB node deployed in each car. Even if the UE moves between cars, from the perspective of a UE inside the train, one of the cells of the mobile IAB node is always more stable than an external macro cell. Furthermore, it is typically assumed that the cells of the mobile IAB node operate on the same frequency. In this case, the existing intra-frequency cell reselection, i.e., the R criterion, works well.

[0163] Observation 1: It is a common configuration for a moving IAB cell to broadcast either a serving frequency priority of "7" or an HSDN cell indication to prevent cell reselection by a UE moving with the IAB cell.

[0164] In subcases B1 and B2, the AS has no way of knowing whether the user will stay on the train or get off. In this case, even if the mobile IAB node broadcasts some information, the UE cannot determine which cell to ultimately reselect, i.e., the mobile IAB node or the fixed macrocell. Therefore, which cell the UE reselects ultimately depends on the radio conditions and frequency priority. In other words, the mobile IAB node needs to restore the serving frequency priority set as observation 1. Therefore, the mobile IAB node needs to broadcast the serving frequency priority. For example, it can do the same as the fixed macrocell layer, or it can stop broadcasting the HSDN cell indication.

[0165] Observation 2: If the UE and the mobile IAB node go down, the UE cannot decide whether to reselect the mobile IAB node or not unless it knows the user's intention, i.e., it depends on the radio conditions.

[0166] Observation 3: It may be typical for a stationary mobile IAB cell to revert to the frequency priority or HSDN cell indication used while mobile (i.e., as in Observation 1).

[0167] However, considering the above observations, one drawback of the current mechanism is that the SIB of a mobile IAB node needs to be modified depending on its mobility status: moving = observation 1, stationary = observation 3. However, this may not be a critical issue to solve.

[0168] Observation 4: One drawback of the current mechanism is that the moving IAB cell needs to change its mobility status, i.e., SIB, between Observation 1 and Observation 3.

[0169] In subcase A2, the UE can continue to camp on the fixed macrocell, following the same logic as in Observation 1. That is, if the RSRP / RSRQ from the macrocell is good enough, the UE will not perform intra-frequency measurements. Also, inter-frequency measurements will not be performed if the macrocell frequency has a higher priority than the mobile IAB node, or if the mobile IAB node broadcasts an HSDN cell indication (and the UE is not in a high mobility state).

[0170] For subcases B3 and B4, cell reselection must be based on radio conditions for the same reasons as in observation 2, and the general configuration of fixed mobile IAB nodes as in observation 3 also applies.

[0171] However, subcases A2, B3, and B4 are desirable behaviors for surrounding UEs. WID explicitly states that it does not perform optimizations targeting surrounding UEs. For subcase B3, after the UE gets on the train, it becomes subcase B1 or B2, but the UE's initial state is still that of a surrounding UE. Therefore, these subcases are outside the scope of Rel-18.

[0172] Enhanced mobility of IAB nodes and their served UEs, including aspects related to group mobility. No optimization for targeting surrounding UEs.

[0173] Observation 5: Optimization for targeting surrounding UEs is outside the scope of WI, but the same configurations as Observations 1 and 3 may be applicable.

[0174] In summary, the existing cell reselection mechanism, i.e., the mechanism based on radio conditions and frequency priorities, continues to work properly, and therefore no enhancements are required for the UE to perform cell reselection.

[0175] It should be noted that HSDN may be useful for subcase A1, but can be supported by mobile IAB nodes without any specification changes.

[0176] Proposal 3: RAN2 should agree that no extensions are necessary for UEs to perform cell reselection to and from mobile IAB nodes, i.e., there is no need to revert the assumption made in the previous meeting about the "1-bit mobile IAB cell type indication."

[0177] RACH-less Handover for Rel-18UE RAN2#119e has reached the following agreement: R2 assumes that a RACH-less procedure may be considered for onboard RRC_CONNECTEDUEs handed over together with mobile IAB nodes (also dependent on UL synchronization assumptions).

[0178] In LTE, RACH-less handover is configured in MobilityControlInfo using the applicable Timing Advance (TA) and uplink grant information as follows:

[0179] Regarding the TA value in a RACH-less handover of a UE during IAB node transition, since the source and target cells are provided by the same "physical cell," the UE is assumed to apply the latest TA value to access the target cell. DU (but via dual "logical" DU), i.e., the "physical" distance from the UE must be the same. Therefore, there is no need to configure an explicit TA value in the UE. On the other hand, if RACH-less handover is intended to be used in other scenarios, such as handover of a mobile IAB-MT, a more general approach such as LTE configuration is required.

[0180] Proposal 4: RAN2 should discuss whether for RACH-less handover of the UE, the UE should implicitly apply the latest TA value or be explicitly configured with an applicable TA value.

[0181] Since the UE needs to send the RRC Reconfiguration Complete within the UL resources granted by the target cell, the UL grant information needs to be configured in the UE.

[0182] Proposal 5: RAN2 needs to agree that for RACH-less handover of the UE, the UL grant information is set by the target IAB donor CU.

[0183] Since RACH-less handover is indicated by the target IAB donor CU during the handover procedure, considering the RRCIE structure of NR, it can be assumed that the RACH-less configuration is included in reconfigurationWithSync in CellGroupConfig.

[0184] Proposal 6: RAN2 should agree that RACH-less handover is configured in the handover command, i.e., reconfiguration with synchronization.

[0185] One question is whether RACH-less handover can also be applied to conditional handover. RAN2#119e agreed that "R2 assumes that CHO or delayed RRC configuration may be the baseline for group mobility," and therefore it is considered useful to support conditional RACH-less handover.

[0186] Proposal 7: RAN2 should discuss whether RACH-less handover can also be configured as a conditional handover, i.e., conditional reconfiguration.

[0187] Enhancements to IAB-MT Mobility Indication of Mobile IAB Node to IAB Donor CU The following agreement has been reached in RAN3#117e: The donor CU must be aware that the IAB node is "mobile".

[0188] In response, RAN2#119bis-e agreed to the following baseline:

[0189] UE capability signaling is the baseline to inform the CU that the MT is of "mobile IAB" type. Further details on the initial mobile IAB indicator (e.g., message 5). Regarding the indication of mobility status / mode, R2 notes that the traditional reports of mobility state (e.g., mobileState-r16) can be reused, and possibly also the current location report from the UE.

[0190] In Rel-16 IAB, the IAB Node Indication is sent via Msg5 and is intended to be used by a donor to select an AMF that supports IAB. Therefore, whether a donor needs to select an AMF that supports Mobile IAB up to RAN3 determines whether to send Mobile IAB Node Indication via Msg5.

[0191] In email discussions, several companies pointed out that real-time mobility status can be obtained by the donor CU through existing measurement reports such as Instant MDT. Such mobility status information is considered useful for predictive mobility control. The reporters clarified that the donor needs the mobile IAB node's instruction to configure the mobile IAB node with the appropriate measurement configuration. However, if the donor CU configures the mobile IAB node after receiving UE capability signaling, this is not a significant issue, and therefore early notification is not justified.

[0192] Therefore, it is up to RAN3 whether an initial mobility IAB indication is required.

[0193] Observation 6: Whether an initial mobile IAB indication in Msg5 is necessary depends on RAN3, for example, whether the donor CU needs to select an AMF that supports mobile IAB.

[0194] Access Restrictions for Mobile IAB Nodes The WID states that a mobile IAB node serves only UEs: - A mobile IAB node must not have any descendant IAB nodes, i.e., it serves only UEs.

[0195] To ensure the requirement, RAN2#119e agreed that not broadcasting the "iab-Support" indication is sufficient to prevent other IAB nodes from accessing the mobile IAB (without further impacting the specification).

[0196] However, it can be said that the agreement was reached without sufficient discussion. In particular, the part "(without further impact on the specification)" raises doubts as to whether it is really sufficient to leave it up to the implementation. Since WID clearly requires that mobile IAB nodes cannot access other mobile IAB nodes, it is necessary to clarify this premise in the specification to avoid confusion in mobile IAB implementations. Therefore, it is recommended that the Stage 2 specification either obtain the above agreement or clarify that "mobile IAB nodes cannot access other mobile IAB nodes in this release."

[0197] Proposal 8: RAN2 should agree to incorporate the Stage 2 specification that if an IAB node acts as a mobile IAB node in this release, it must not set the IAB support IE in the SIB.

[0198] Another limitation was discussed in RAN2#119bis-e and was noted to require further study: Whether to introduce a fixed network broadcasting indication that it supports mobile IAB (targeting mobile IABMT) requires further study.

[0199] Several companies have noted that "whether or not network instructions to a mobile IAB node are required may depend on whether the mobile IAB node can / should camp on / connect to a regular IAB-capable cell." Assuming the presence of a traditional IAB donor in the network, there are three releases of IAB, and different releases support different transition mechanisms: intra-CU topology adaptation in Rel-16, inter-CU topology adaptation with partial transition in Rel-17, and inter-CU transition with full transition in Rel-18.

[0200] Thus, technically, a mobile IAB node can connect with a Rel-16 donor if it is only moving nearby (i.e., within cells belonging to the same donor CU), but the mobile IAB node must connect to a Rel-17 or Rel-18 donor if the Rel-18 donor moves farther (i.e., between cells belonging to different donor CUs), in other words, the former mobile IAB node can be considered merely a fixed IAB node from a functional point of view.

[0201] Observation 7: A mobile IAB node can connect with a Rel-16 donor if it only moves nearby, but if it moves far away, the mobile IAB node needs to connect with a Rel-17 or Rel-18 donor.

[0202] In this sense, some kind of "support mobile IAB" information needs to be broadcast by the parent node, but it is questionable whether it is possible to determine the cells to which a mobile IAB node can connect. Based on such a one-bit indication, for example, the indication could be associated with the area to which the mobile IAB node can move. However, it may also mean that the mobile IAB node needs to know the area to which it moves (or whether it is considered a fixed IAB node), for example, through an OAM configuration. Furthermore, it is worth considering whether there are other cases in which a mobile IAB node can connect to a parent node that does not broadcast an indication. For example, the case in which the mobile IAB node cannot find a parent node that broadcasts an indication. Therefore, RAN2 should discuss in detail what the indication means.

[0203] Proposal 9: RAN2 should agree that some kind of "supports mobile IAB" indication be introduced. Further study is needed as to whether it is simply a one-bit indication and / or whether there is a condition that mobile IAB nodes can access parent nodes that do not broadcast the indication.

Claims

1. A communication control method used in a cellular communication system, comprising: a relay node notifying an offset value for a mobile relay node; and a user equipment executing an intra-frequency cell reselection procedure using the offset value for the mobile relay node. The communication control method.

2. The notifying includes the relay node notifying different offset values for the mobile relay node according to whether the relay node is a mobile relay node or a relay node other than the mobile relay node. The communication control method according to Claim 1.

3. The executing includes the user equipment changing an application method of the offset value for the mobile relay node according to whether a serving cell and an adjacent cell are cells of a mobile relay node. The communication control method according to Claim 1.

4. The changing includes: when the user equipment camps on a cell of a relay node other than the mobile relay node, subtracting the offset value for the mobile relay node from a reference signal reception power for the cell of the mobile relay node; and when the user equipment camps on a cell of the mobile relay node, adding the offset value for the mobile relay node to the reference signal reception power for the cell of the mobile relay node. The communication control method according to Claim 3.

5. In the adding, instead of adding the offset value for the mobile relay node, the user equipment subtracts the offset value for the mobile relay node from a reference signal reception power for a cell of a relay node other than the mobile relay node. The communication control method according to Claim 4.

6. The changing includes the user equipment executing the intra-frequency cell reselection procedure without using the offset value for the mobile relay node when the user equipment camps on a cell of the mobile relay node and the adjacent cell is also a cell of the mobile relay node. The communication control method according to Claim 3.

7. The communication control method according to Claim 1, further comprising the user equipment executing a cell reselection procedure using the offset value for the mobile relay node. The communication control method according to Claim 1.

8. The communication control method according to Claim 1, further comprising the user equipment executing an inter-frequency cell reselection procedure using the offset value for the mobile relay node. The communication control method according to Claim 1.

9. ​ The mobile relay node further broadcasts mobile relay node cell type information indicating that the node is the mobile relay node. The communication control method according to claim 1.

10. A communication control method for use in a cellular communication system, comprising: receiving, by a user equipment, from a high speed dedicated network (HSDN) cell, HSDN cell information indicating that the cell is an HSDN cell, and mobile relay node cell type information indicating that the cell is a cell of a mobile relay node; performing an inter-frequency cell reselection procedure when the user equipment is in a low-motion state without considering the cell as a lowest-priority cell. Communication control method.

11. The method further includes the user equipment receiving a frequency priority of a frequency used in the cell; The performing includes the user equipment performing the inter-frequency cell reselection procedure using the frequency priority of the cell. The communication control method according to claim 10.

12. A user device, comprising: a receiving unit for receiving an offset value for a mobile relay node broadcast by a relay node; a control unit that performs an intra-frequency cell reselection procedure using the mobile relay node offset value; User equipment.

13. A user device, comprising: a receiving unit for receiving from the cell high speed dedicated network (HSDN) cell information indicating that the cell is an HSDN cell and mobile relay node cell type information indicating that the cell is a mobile relay node cell; a control unit that performs an inter-frequency cell reselection procedure without considering the cell as a lowest priority cell when in a low-speed movement state. User equipment.