User equipment, node, and communication method
Patent Information
- Application Number
- JP2025165149
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-10-01
- Publication Date
- 2026-09-09
Smart Images
Figure 2026144943000001_ABST
Abstract
Description
[[Technical Field]]
[0001] The present invention relates to a user equipment, a node, and a communication method. [[Background Art]]
[0002] As a new form of mobile phone line replacing NR (New Radio), which is the 5th generation (5G) standard developed by the 3rd Generation Partnership Project (3GPP (registered trademark, the same applies hereinafter)), a standardization project for mobile communication systems, a device configuration called cell-free massive MIMO (Multi Input Multi Output) has been studied. Cell-free massive MIMO adopts a configuration in which base stations are arranged more densely than in the prior art, and is a method that achieves both communication quality and power saving by activating only the most appropriate minimum necessary base stations in response to communication requests from terminals.
[0003] On the other hand, mobile lines are required to have the characteristic of "being connected anytime, anywhere, quickly". In view of this, even if cell-free massive MIMO is a method that only activates the minimum necessary base stations, it is expected that macro base stations that always operate as in the past and cover the entire area will continue to exist in the future. Furthermore, it is expected that the operation of these base stations will be collectively managed by a central control unit (CU) in accordance with current standards.
[0004] Under the above-described situation setting, the procedure for activating a small base station that is in sleep state during normal time is as follows. First, a macro station pre-connected to a terminal receives a request for a high-quality line from the terminal. Next, a small base station suitable for communication with the terminal and a communication propagation path are searched. As a result of the search, a link is established between the selected small base station and the terminal. On the other hand, small base stations other than the selected small base station are put back to sleep. As a result, only the selected small base station is activated.
[0005] In the procedure for searching for small base stations and communication propagation paths suitable for communication with terminals, conventional methods (radiation of reference signals) require the temporary activation of each base station. Furthermore, reference signals may interfere with each other in densely populated base stations. Therefore, there is a need for technology that can complete the procedure for searching for small base stations and communication propagation paths suitable for communication with terminals in a power-efficient and stable manner. [Prior art documents] [Non-patent literature]
[0006] [Non-Patent Document 1] 3GPP Technical Specification: TS38.401 V18.4.0(2024-12) [Overview of the project]
[0007] The user device according to the first embodiment is a user device that performs wireless communication with a primary node and a secondary node using dual connectivity in a mobile communication system, and receives first information indicating an adjacent cell from the primary node, selects the secondary node to be woken from sleep based on the first information, and transmits second information indicating the adjacent cell that the user device wants to wake from sleep to the primary node.
[0008] A node according to the second embodiment is a node that operates in a mobile communication system in which a user device performs wireless communication using dual connectivity, wherein the node transmits first information indicating an adjacent cell to the user device, receives second information from the user device indicating an adjacent cell that the user device wants to wake up, and wakes up the adjacent cell based on the received second information.
[0009] A third aspect of the communication method is a communication method used in a user device that performs wireless communication with a primary node and a secondary node using dual connectivity in a mobile communication system, comprising the steps of: receiving first information indicating an adjacent cell from the primary node; selecting a secondary node to be woken from sleep based on the first information; and transmitting second information indicating an adjacent cell that the user device wishes to wake from sleep to the primary node.
[0010] A fourth aspect of the communication method is a communication method used in a node that performs wireless communication with a user device using dual connectivity in a mobile communication system, comprising the steps of: transmitting first information indicating an adjacent cell to the user device; receiving second information from the user device indicating an adjacent cell that the user device wants to wake up; and waking up the adjacent cell based on the received second information. [Brief explanation of the drawing]
[0011] [Figure 1] This is a diagram showing an example configuration of a mobile communication system according to the embodiment. [Figure 2] This figure shows an example of the protocol stack configuration for a U-plane wireless interface that handles data. [Figure 3] This diagram shows an example of a protocol stack configuration for a C-plane wireless interface that handles signaling (control signals). [Figure 4] This is a diagram illustrating a terahertz (THz) wave cell according to an embodiment. [Figure 5] This is a diagram illustrating dual connectivity (DC) according to an embodiment. [Figure 6] This figure shows an example configuration of a wireless access network (RAN) according to the embodiment. [Figure 7] This figure shows an example configuration of a UE (User Equipment) according to the embodiment. [Figure 8] This figure shows an example of a node configuration according to the embodiment. [Figure 9] It is a diagram showing an example of system operation according to the first embodiment. [Figure 10] It is a diagram showing an example of system operation according to the first embodiment. [Figure 11] It is a diagram showing an example of coordinated scheduling according to the first embodiment. [Figure 12] It is a diagram showing an example of transmission timing of a synchronization signal block (SSB) beam according to the first embodiment. [Figure 13] It is a diagram showing another example of transmission timing of a synchronization signal block (SSB) beam according to the first embodiment. [Figure 14] It is a diagram showing an example of system operation according to a modification of the first embodiment. [Figure 15] It is a diagram showing an example of system operation according to a modification of the first embodiment. [Figure 16] It is a diagram showing an example of system operation according to the second embodiment. [Figure 17] It is a diagram showing an example of system operation according to the second embodiment. [Figure 18] It is a diagram showing an example of system operation according to the third embodiment. [Figure 19] It is a diagram showing an example of system operation according to the third embodiment. [Figure 20] It is a diagram showing an example of system operation according to the fourth embodiment. [Figure 21] It is a diagram showing an example of system operation according to the fourth embodiment. DESCRIPTION OF EMBODIMENTS
[0012] Hereinafter, a mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar reference numerals are assigned to the same or similar parts.
[0013] (1) First Embodiment The first embodiment will be described with reference to FIGS. 1 to 15.
[0014] (1.1) Example of system configuration Figure 1 shows an example configuration of a mobile communication system according to an embodiment. The mobile communication system according to the embodiment is a system compliant with the 3GPP standard. For example, the mobile communication system according to the embodiment may be a fifth-generation (5G) system or a sixth-generation (6G) system.
[0015] The mobile communication system comprises a network (NW) 1 and a user device (UE) 100. The UE 100 is a mobile communication device that performs wireless communication with the NW 1. The UE 100 may be any device used by a user, such as a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC (Personal Computer), a communication module (including a communication card or chipset), a sensor or a device attached to a sensor, a vehicle or a device attached to a vehicle (Vehicle UE), or an aircraft or a device attached to an aircraft (Aerial UE).
[0016] NW1 includes the Radio Access Network (RAN) 10 and the Core Network (CN) 20. When the mobile communication system is a 5th Generation System (5GS), RAN 10 is referred to as NG-RAN (Next Generation Radio Access Network) and CN 20 is referred to as 5GC (5G Core Network).
[0017] RAN10 includes multiple nodes 200 (nodes 200a to 200c in the illustrated example). The nodes 200 are interconnected via internode interfaces. Nodes 200 are also referred to as base stations. Nodes 200 consist of a CU (Central Unit), a DU (Distributed Unit), and a RU (Radio Unit) (i.e., functionally separated), and the two units may be connected by a fronthaul interface. If the mobile communication system is 5GS, the nodes 200 are referred to as gNBs, the internode interfaces as Xn interfaces, and the fronthaul interfaces as F1 interfaces.
[0018] Each node 200 manages one or more cells. Node 200 performs wireless communication with UE100s that have established a connection with its own cell. Each node 200 has wireless resource management (RRM) functions, user data routing functions (also simply referred to as "data"), and measurement and control functions for mobility control and scheduling. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate the function or resource that performs wireless communication with the UE100. One cell belongs to one carrier frequency (also simply referred to as "frequency").
[0019] CN20 includes CN device 300. CN device 300 may include a C-plane device corresponding to the control plane (C-plane) and a U-plane device corresponding to the user plane (U-plane). The C-plane device performs various mobility controls and paging for UE100. The C-plane device communicates with UE100 using NAS (Non-Access Stratum) signaling. The U-plane device controls data transfer. When the mobile communication system is 5GS, the C-plane device is called AMF (Access and Mobility Management Function), the U-plane device is called UPF (User Plane Function), and the interface between node 200 and CN device 300 is called the NG interface.
[0020] Figure 2 shows an example of the protocol stack configuration for a U-plane radio interface that handles data.
[0021] A U-plane radio interface protocol, for example, includes a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) layer.
[0022] 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 UE100 and the PHY layer of Node 200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from Node 200 over the physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a Radio Network Temporary Identifier (RNTI) and acquires the successfully decoded DCI as the DCI addressed to its own UE. The DCI transmitted from Node 200 has a CRC parity bit added that has been scrambled by the RNTI.
[0023] The MAC layer performs data priority control and retransmission processing using Hybrid ARQ (HARQ). Data and control information are transmitted between the MAC layer of UE100 and the MAC layer of Node 200 via the transport channel. The MAC layer of Node 200 includes a scheduler. The scheduler determines the transport format for the up and down links (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to UE100.
[0024] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of UE100 and the RLC layer of Node 200 via a logical channel.
[0025] The PDCP layer performs header compression / decompression, encryption / decryption, etc.
[0026] The SDAP layer maps IP flows, which are the units for QoS control performed by CN20, to wireless bearers, which are the units for QoS control performed by AS (Access Stratum). Note that if the RAN is connected to the EPC (Evolved Packet Core), SDAP is not required.
[0027] Figure 3 shows an example of the protocol stack configuration for a C-plane wireless interface that handles signaling (control signals).
[0028] The protocol stack of the C-plane radio interface, for example, includes an RRC (Radio Resource Control) layer and a NAS (Non-Access Stratum) layer instead of the SDAP layer shown in Figure 2.
[0029] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of Node 200. The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. If there is a connection (RRC connection) between the RRC of UE100 and the RRC of Node 200, UE100 is in the RRC connected state. If there is no connection (RRC connection) between the RRC of UE100 and the RRC of Node 200, UE100 is in the RRC idle state. If the connection between the RRC of UE100 and the RRC of Node 200 is suspended, UE100 is in the RRC inactive state.
[0030] The NAS layer (also simply referred to as "NAS"), located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the NAS layer of the UE100 and the NAS layer of the CN device 300. The UE100 also has an application layer in addition to the wireless interface protocol. Furthermore, the layer below the NAS layer is called the AS layer (also simply referred to as "AS").
[0031] (1.2) DC using a terahertz wave cell Figure 4 is a diagram illustrating a terahertz (THz) wave cell according to an embodiment.
[0032] The mobile communication system according to this embodiment may be a 6G system. 6G is expected to utilize terahertz (THz) waves. A cell operating with THz waves is referred to as a THz cell. Compared to millimeter waves (mmW), THz waves have even stronger directivity, higher free-space loss, and are more susceptible to atmospheric and rainfall influences. Therefore, THz cells can be ultra-small cells.
[0033] In the illustrated example, the diameter of the coverage area of a THz wave cell is approximately 10 m, the diameter of the coverage area of a mmW cell operating at mmW is approximately 100 m, and the diameter of the coverage area of a macrocell is approximately 1000 m. Under these assumptions, for example, a UE100 moving at 60 km / h would pass through the coverage area of each THz wave cell in approximately 599 ms.
[0034] Dual connectivity (DC) is one method for stably controlling small cells in a mobile communication system. Figure 5 is a diagram illustrating dual connectivity (DC) according to an embodiment. In this embodiment, it is assumed that a THz wave cell is used as a cell in a secondary cell group (SCG). Furthermore, a THz wave cell may also be used as a secondary cell (SCell) in a master cell group (MCG). However, a mmW cell may be used instead of a THz wave cell.
[0035] A UE100 in RRC connected state can be configured as a DC. In a DC, the UE100 communicates wirelessly with the Master Cell Group (MCG) managed by the Master Node (MN) 200M and the Secondary Cell Group (SCG) managed by the Secondary Node (SN). The MN200M and SN200S are connected to each other via an inter-node interface. When MN200M and SN200S are not distinguished, they are simply referred to as Node 200. The MN200M is also called the Master gNB (MgNB) when it is a 5G / NR node. The SN200M is also called the Secondary gNB (SgNB) when it is a 5G / NR node.
[0036] For example, when the MN200M sends a predetermined message (e.g., an SN Addition Request message) to the SN200S, and the MN200M sends an RRC Reconfiguration message to the UE100, the SCG is set to the UE100 and the DC starts. In the DC, the UE100, in an RRC connected state, is allocated radio resources from the schedulers of the MN200M and SN200S, and performs wireless communication using the radio resources of the MN200M and SN200S.
[0037] The MN200M may have a control plane connection to the CN20. The MN200M provides the primary radio resources for the UE100. The MN200M manages the MCG, a group of serving cells associated with the MN200M. The MCG has a primary cell (PCell) and optionally one or more secondary cells (SCells). On the other hand, the SN200S does not need to have a control plane connection to the CN20. The SN200S provides additional radio resources to the UE100. The SN200S manages the SCG, a group of serving cells associated with the SN200S. The SCG has a primary and secondary cell (PSCell) and optionally one or more SCells. Note that the PCell of the MCG and the PSCell of the SCG are sometimes referred to as special cells (SpCells).
[0038] The mobile communication system supports the activation and deactivation of the SCG to reduce the power consumption of the UE100 when DC is configured. SCG activation / deactivation can be instructed by an RRC Reconfiguration message from the MN200M to the UE100. While the SCG is deactivated, all SCG SCells are inactive. While the SCG is deactivated, the UE100 does not need to transmit Physical Uplink Shared Channel (PUSCH), Sounding Reference Signal (SRS), and Channel Quality Index (CSI) reports via the SCG. Furthermore, while the SCG is deactivated, the UE100 does not need to monitor the Physical Downlink Control Channel (PDCCH) or receive Downlink Shared Channel (DL-SCH) via the SCG. However, the UE100 can continue to perform Radio Link Monitoring (RLM) and Measurement Reporting for PSCells. When activating the SCG, the UE100 can skip the random access procedure if timing advance (TA) with the PSCell is enabled.
[0039] Figure 6 shows an example configuration of RAN10 according to this embodiment. RAN10 includes MN200M as multiple nodes 200 and one or more SN200S. Note that only one of the one or more SN200S is shown in Figure 6. MN200M includes CU260, macro station 270M, and small station 270S. Macro station 270M included in MN200M consists of macro station DU and macro station RU. Macro station 270M included in MN200M manages the MCG's PCell. Small station 270S included in MN200M consists of small station DU and small station RU. Small station 270S included in MN200M manages the MCG's SCell.
[0040] Each of the SN200S includes a CU260 and a small station 270S (neither of which are shown in the diagram). The small station 270S included in the SN200S consists of a small station DU and a small station RU. The small station 270S included in the SN200S manages the SCG's PSCell and SCell. In DC, when UE100 connects to SCG, UE100 connects to at least the PSCell. When UE100 connects to SCG, it may also connect to the SCG's SCell along with the PSCell.
[0041] In this embodiment of DC, UE100 performs wireless communication with the MCG's PCell managed by the macro station DU connected to the CU260 included in MN200M, and with the SCG's PSCell or SCell managed by the small station DU included in SN200S. In other words, DC is performed using the PCell owned by the MCG and the PSCell or SCell owned by the SCG.
[0042] (1.3) Example of user device configuration Figure 7 shows an example configuration of UE100 (user device) according to the embodiment.
[0043] UE100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit 140 that performs wireless communication with the node 200.
[0044] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130. The transmitting unit 120 performs various types of transmission under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmitted signal) output by the control unit 130 into a radio signal and transmits it from the antenna.
[0045] The control unit 130 performs various controls and processes in the UE100. The operation of the UE100 described above and below may also be controlled by the control unit 230. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processes.
[0046] (1.4) Example of node configuration Figure 8 shows an example configuration of node 200 (base station) according to the embodiment. Node 200 may be MN200M or SN200S.
[0047] Node 200 includes a transmitter 210, a receiver 220, a control unit 230, and a network communication unit 240. The transmitter 210 and receiver 220 constitute a wireless communication unit 250 that performs wireless communication with UE 100.
[0048] The transmitting unit 210 performs various types of transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna. The receiving unit 220 performs various types of receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230.
[0049] The control unit 230 performs various controls and processes at node 200. The operation of node 200 described above and below may be controlled by the control unit 230. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processes.
[0050] The NW communication unit 240 is connected to an adjacent node via an inter-node interface. The NW communication unit 240 is connected to the CN device 300 via a node-CN interface.
[0051] Node 200M, configured in this way, is a network node having a central unit and multiple distributed units. The central unit transmits the transmission timing of the synchronization signal block to the second distributed unit. CU260 is an example of a central unit. Macro station 270M and small station 270S are examples of multiple distributed units. Small station 270S is an example of a second distributed unit.
[0052] With the above configuration, node 200M can transmit the transmission timing of the synchronization signal block to the second distributed unit, enabling the procedure of searching for a communication path with small station 270S, which is suitable for communication with UE100, to be completed in a power-efficient and stable manner.
[0053] The mobile communication system according to this embodiment is a mobile communication system having a central unit and a plurality of distributed units. Furthermore, CU260 is a central unit included in the mobile communication system having a central unit and a plurality of distributed units.
[0054] Furthermore, the small station 270S is a distributed unit included in a mobile communication system that has a central unit and multiple distributed units. The small station 270S receives the transmission timing of the Synchronization Signal Block (SSB) from the central unit. The small station 270S transmits the SSB based on the SSB transmission timing.
[0055] (1.5) System Operation Example Figure 9 is a diagram showing an example of system operation according to the first embodiment. The CU260 shown in Figure 9 is the CU260 included in SN200S. In Figure 9, the CU260 included in MN200M is omitted. The macro station 270M shown in Figure 9 is the macro station 270M included in MN200M. In DC, when the CU260 included in SN200S and the macro station 270M included in MN200M communicate, the communication is conducted via the CU260 included in MN200M. The small station 270S shown in Figure 9 is the small station 270S included in SN200S. In the system operation according to the first embodiment, the CU260 included in the SN200S transmits the SSB transmission timing to each of the multiple small stations 270S included in the SN200S.
[0056] In the following explanation, the CU260 included in SN200S will be simply referred to as "CU260". The small station 270S included in SN200S will be simply referred to as "small station 270S". The macro station 270M included in MN200M will be simply referred to as "macro station 270M". Also, in the following explanation, "small station 270S" refers to any one of small stations 270S-1 to 270S-N. "Multiple small stations 270S" refers to two or more of small stations 270S-1 to 270S-N.
[0057] In step S10, the UE100 is pre-connected to the PCell of the macro station 270M.
[0058] In step S20, small stations 270S-1 through 270S-N are in sleep mode.
[0059] In step S30, UE100 transmits a request for radio quality conditions to macro station 270M. UE100 transmits this request in the UCI sent via PUCCH. Alternatively, UE100 may transmit this request in a PDCP Control PDU or RRC message. Radio quality conditions include, for example, high throughput data transmission and reception in both UL and DL. Macro station 270M receives the request for radio quality conditions from UE100. The request for radio quality conditions is an example of a notification transmitted from UE100 to macro station 270M. Therefore, UE100 transmits a notification to the master node.
[0060] In step S40, the macro station 270M sends a message to the CU260 notifying it of the traffic congestion status. For example, the macro station 270M sends the traffic congestion status to the CU260 in a Resource Status Request message. Thus, the macro station 270M that constitutes the PCell notifies the CU260 of information indicating the usage of radio resources. The CU260 receives a message from the macro station 270M notifying it of the traffic congestion status.
[0061] In step S50, CU260 instructs the small stations 270S to wake up. Therefore, having received information indicating the usage of radio resources, CU260 instructs multiple small stations 270S near UE100 to wake up. Based on the location information of UE100, CU260 selects small stations 270S located within a specific range. CU260 instructs the selected small stations 270S to wake up. The selected small stations 270S receive the instruction to wake up from CU260. In Figure 9, small stations 270S-1 to 270S-N are shown as small stations 270S-1 to 270S-N selected by CU260 as being located within a specific range.
[0062] This section details the process by which CU260 selects a small station 270S to wake from sleep based on the location information of UE100. For example, CU260 first selects a small station 270S that is close to UE100. In this case, CU260 may select a small station 270S whose distance from UE100 is less than or equal to a predetermined distance. Alternatively, CU260 may select a predetermined number of small stations 270S in order of their shortest distance from UE100.
[0063] CU260 selects a set of small stations 270S that are close to UE100 and whose SSB searches in step S120 (described later) are less likely to interfere with each other. Less interference in SSB searches means that the synchronization signal-to-interference ratio (SS-SIR) of the synchronization signals received by UE100 during the SSB search is not likely to deteriorate. For example, CU260 selects small stations 270S that are close to UE100 and whose operating frequency bands are different from each other. The operating frequency band is the frequency band of the cell used by the small station 270S as the SCG's PSCell or SCell. However, if interference between SSBs can be avoided by the interference avoidance process in the SSB search (described later), CU260 may select small stations 270S that are close to UE100 and whose operating frequency bands are the same.
[0064] Furthermore, CU260 determines the current position of UE100 based on known technologies. CU260 determines the current position of UE100 based on methods such as MDT (Minimalization of Drive tests), Timing Advance, or Proximity Indication.
[0065] Furthermore, the processing capacity of UE100 may be notified in advance from UE100 to CU260 via macro station 270M. In that case, CU260 may limit the number of small stations 270S selected to be instructed to wake from sleep mode, depending on the processing capacity of UE100.
[0066] In step S60, both the DU and RU are activated at small stations 270S-1 through 270S-N, each of which has received a wake-up instruction. The RU activates the transmitter and receiver.
[0067] In step S70, small stations 270S-1 and 270S-N each send a request for operational configuration to CU260. Small stations 270S-1 and 270S-N each send this request, for example, in an F1 SETUP REQUEST message.
[0068] In step S80, CU260 transmits operational settings from small station 270S-1 to small station 270S-N. CU260 transmits these settings, for example, in an F1 SETUP RESPONSE message.
[0069] In step S90, CU260 determines the SSB settings for small stations 270S-1 through 270S-N. The SSB settings include an activated SSB list and an SSB time sequence list.
[0070] The activated SSB list is beam information that identifies SSB beams transmitting SSB. The activated SSB list includes an SSB index, which is an identifier indicating the SSB beam requested to be activated. The SSB search direction is specified by the SSB index.
[0071] The SSB time sequence list indicates the transmission timing of SSB. The SSB time sequence list indicates the time when the SSB beam radiation begins and the order in which the SSB beams are emitted. Therefore, in this embodiment, the transmission timing of SSB is indicated by the time when the first SSB to be transmitted among multiple SSBs begins to be transmitted and the transmission order of the multiple SSBs. CU260 determines the SSB beam radiation start time and the SSB beam radiation order so that SSBs do not interfere with adjacent small stations 270S and the SS-SIR of the synchronization signal received by UE100 in SSB search does not decrease. Determining the SSB beam radiation start time and the SSB beam radiation order so that SSBs do not interfere with adjacent small stations 270S is called cooperative scheduling. Details of cooperative scheduling will be described later.
[0072] In step S100, CU260 transmits the SSB configuration determined in step S90 to each of the small stations 270S-1 through 270S-N. Thus, CU260 transmits the SSB transmission timing to each of the multiple small stations 270S. CU260 transmits the SSB configuration, for example, in a gNB-CU CONFIGURATION UPDATE message. Each of the small stations 270S-1 through 270S-N receives the SSB configuration. If the received SSB configuration includes an activated SSB list, small station 270S-i activates only the SSB beams indicated by the SSB indices included in the activated SSB list.
[0073] As described above, in this embodiment, beam information indicating the SSB beam to transmit the SSB (for example, an activated SSB list) is specified separately from the SSB transmission timing (for example, an SSB time sequence list). CU260 transmits the beam information along with the SSB transmission timing to the small station 270S. Note that the beam information and the SSB transmission timing may be specified as a single piece of information. For example, since the SSB time sequence list specifies the transmission order for multiple SSBs, it includes information about the SSB beams to be transmitted. Therefore, the beam information indicating the SSB beam and the SSB transmission timing may be specified by the SSB time sequence list. In that case, the activated SSB list is omitted from the SSB settings.
[0074] In step S110, small station 270S-1 to small station 270S-N each send a message to CU260 indicating that they have activated the SSB beam indicated by the SSB index shown in the SSB configuration. Small station 270S-1 to small station 270S-N each send this message, for example, in a gNB-CU CONFIGURATION UPDATE ACKNOWLEDGE.
[0075] In step S120, UE100 performs an SSB search. Small stations 270S-1 through 270S-N each emit an SSB beam based on the time and order indicated by the SSB settings received from CU260 in step S100. Thus, multiple woken small stations 270S transmit SSB based on their SSB transmission timing. Here, small stations 270S transmit SSB based on their SSB transmission timing via the activated SSB beam among the SSB beams indicated by the beam information. The SSB includes, for example, a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), and a Master Information Block (MIB).
[0076] The UE100 receives SSB signals from small stations 270S-1 and 270S-N. The UE100 measures the RSRQ (Reference Signal Received Quality) of the synchronization signal contained in each SSB. The UE100 selects the SSB with the highest measured RSRQ from among the received SSBs. Based on the combination of PSS and SSS contained in the selected SSB, the UE100 determines that small station 270S, indicated by the Physical Cell Identity (PCI), is the optimal PSCell or SCell. The following describes an example in which the UE100 determines that small station 270S-1 is the optimal PSCell or SCell among small stations 270S-1 and 270S-N. Note that even when the UE100 receives multiple beams, it can perform the RSRQ measurement process in parallel as long as the frequency bands of the multiple beams are different from each other. The optimal PSCell or SCell is one that is suitable for communication with the UE100.
[0077] In step S130, UE100 determines that small station 270S-1 is the optimal PSCell or SCell and transmits a Physical Random Access Channel (PRACH) to small station 270S-1. Small station 270S-1 receives the PRACH from UE100. Upon receiving the PRACH, small station 270S-1 transmits a random access response to UE100.
[0078] In step S140, UE100 connects to small station 270S-1 as a PSCell or SCell. UE100 sends an RRC Connection Request message to small station 270S-1. Small station 270S-1 sends an RRC connection message to UE100. Thus, at least one of the multiple small stations 270S (small station 270S-1) receives a PRACH from UE100 and establishes a connection with UE100.
[0079] In step S150, CU260 instructs the small stations 270S (from small station 270S-2 to small station 270S-N) that UE100 did not connect to in step S140 to go to sleep. Therefore, CU260 instructs the small stations 270S that did not establish a connection with UE100 to go to sleep. Small stations 270S-2 to small stations 270S-N each receive a sleep instruction from CU260.
[0080] In step S160, small stations 270S-2 to 270S-N, having received a sleep command, go back to sleep. Small stations 270S-2 to 270S-N then shut down their transmitters and receivers, respectively.
[0081] In step S170, the small station 270S-1 performs high-throughput data transmission and reception with the UE100 in both UL and DL. The processing in step S170 includes, for example, the following: The small station 270S-1 transmits the SRS resource settings to the UE100. The small station 270S-1 transmits a Channel Status Information Reference Signal (CSI-RS) to the UE100. The UE100 measures the CSI-RS resources and calculates the precoder to be used for SRS transmission based on the CSI-RS resource measurement. The UE100 applies the calculated precoder and transmits the SRS to the small station 270S-1. Based on the received SRS, the small station 270S-1 determines one or more SRIs (SRS Resource Indicators) corresponding to the precoder to be used for PUSCH transmission. The small station 270S-1 transmits the determined one or more SRIs to the UE100. The UE100 transmits PUSCH to small station 270S-1 using the same antenna port as the SRS antenna port.
[0082] Here, we will explain the details of cooperative scheduling. Figure 11 shows an example of cooperative scheduling according to this embodiment. In the example shown, small station 270S-1 and small station 270S-2 are adjacent to each other and use the same frequency band.
[0083] The SSB index specifies the synchronous signal block beam (SSB beam), which is the beam transmitting SSB. It is assumed that interference is likely to occur if the SSB radiated by small station 270S-1 with an SSB index of "i1" and the SSB radiated by small station 270S-2 with an SSB index of "j1" are radiated simultaneously. Similarly, interference is likely to occur if the SSB radiated simultaneously by SSB indexes of "i2" and "j2", "i3" and "j3", and "i4" and "j4". For other combinations of SSB indices radiated by small station 270S-1 and small station 270S-2, interference is unlikely even if they are radiated simultaneously.
[0084] The direction in which the SSB beam is emitted is predetermined for each base station. The CU260 knows in advance which small stations will cause interference if they simultaneously emit SSB beams.
[0085] In this embodiment, the order of SSB radiated by small station 270S-1 and the order of SSB radiated by small station 270S-2 are set to the following order. This prevents interference between the SSB radiated by small station 270S-1 and small station 270S-2, even if the operating frequency bands of adjacent small stations 270S-1 and 270S-2 are the same.
[0086] CU260 sets "i1, i2, i3, i4" as the SSB index for small station 270S-1. Furthermore, in the SSB time sequence list for small station 270S-1, CU260 sets the SSB beam emission start time to time t0 and the SSB beam emission order to "i1, i2, i3, i4" using the SSB index. According to this SSB time sequence list, the SSB beam is emitted at a predetermined cycle in the order of "i1, i2, i3, i4" relative to time t0. Time t0 is selected by CU260 from, for example, predetermined transmission times based on the SSB transmission cycle. The SSB transmission cycle is set by the telecommunications carrier when the base station is installed. Note that time t0 may be specified by CU260 instead of being selected from the predetermined transmission times.
[0087] On the other hand, CU260 sets "j1, j2, j3, j4" as the SSB index for small station 270S-2. Also, in the SSB time sequence list for small station 270S-2, CU260 sets the start time of SSB beam emission to time t0 and sets the order of SSB beam emission to "j3, j4, j1, j2" by SSB index. According to this SSB time sequence list, the SSB beam is set to be emitted in the order of "j3, j4, j1, j2" at a predetermined period, based on time t0.
[0088] As described above, when the SSB beam emission start time and emission order are set, Figure 12 shows the emission times of the SSB beams emitted from the RU of small station 270S-1 and the RU of small station 270S-2, respectively.
[0089] Furthermore, for an SSB index specified by CU260, the small station 270S does not have to activate all SSB beams specified by that SSB index. In other words, there may be SSB beams among those specified by the SSB index that are not activated. If the DU does not activate an SSB beam specified by the SSB index, for example, there may be a fault in the RU. Another example is when the DU knows the location of UE100 in more detail and determines that there is no need to radiate an SSB beam in any direction other than that of UE100.
[0090] For example, if the SSB indices "j1, j2, j3, j4" are specified, small station 270S-2 may only radiate the SSB beams for the SSB indices "j1, j2, j3". In other words, the SSB beam for the SSB index "j4" will not be radiated. In this case, Figure 13 shows the radiation times of the SSB beams radiated from the RU of small station 270S-1 and small station 270S-2, respectively. Even if the DU does not activate the SSB beams specified by the SSB index, it is preferable not to place an SSB index in the section for SSB index "j4", which is not actually radiated, in order to avoid interference between SSB beams. If the radiation times for SSB indices "j1" and "j2" are shifted forward in the section for SSB index "j4" without leaving a gap, coordination will be disrupted and SSB interference will be more likely.
[0091] Furthermore, if the timing of SSB emission is set so that SSB beams are not emitted simultaneously by small stations 270S-1 and 270S-2, without setting the order of SSB beam emission based on coordinated scheduling, the SSB search will take longer than if the SSB beams were emitted simultaneously. For example, if small station 270S-2 emits four SSB beams after small station 270S-1 has emitted four SSB beams, the SSB search will take longer than an SSB search based on coordinated scheduling. However, it is sufficient that small stations 270S-1 and 270S-2 are set to emit at least one pair of SSB beams simultaneously. For the remaining SSB beams, the timing of emission between small stations 270S-1 and 270S-2 may differ.
[0092] The number of SSBs and the transmission cycle of the SSBs are set by the telecommunications carrier when the base station is installed. In this embodiment, as mentioned above, there are four SSBs. The transmission cycle is selected from, for example, 5ms, 10ms, 20ms, 40ms, 80ms, or 160ms.
[0093] In cooperative scheduling, the above-described order of SSB beam emission is just one example; any order is acceptable as long as interference is avoided. Furthermore, although the above description described the case where there are two small 270S stations, similarly, even if there are three or more small 270S stations, any order of SSB beam emission is acceptable as long as interference is avoided.
[0094] As described above, in cooperative scheduling, when CU260 instructs each of multiple small stations 270S with the same frequency band to wake up, it transmits to each of the multiple small stations 270S a transmission timing that prevents the SSB beams transmitting SSB among them from interfering with each other. This configuration allows UE100 to perform an SSB search in a shorter time compared to when cooperative scheduling is not implemented.
[0095] In this embodiment, an example has been described in which the SSB transmission timing is indicated by the time when the first SSB among multiple SSBs is transmitted (SSB beam emission start time) and the transmission order of multiple SSBs, but it is not limited to this. An example has been described in which the SSB beam emission start time and the emission order are set, but it is not limited to this. The SSB transmission timing may also be indicated by the transmission order of the SSBs alone. In that case, the SSB beam emission start time is set in advance by the telecommunications carrier along with the SSB transmission cycle, etc., when the base station is installed. Therefore, the SSB transmission timing is indicated by at least the transmission order of the SSBs. In addition, the SSB beam emission time may be specified as the SSB transmission timing.
[0096] (1.6) System operation example relating to a modified version of the first embodiment Referring to Figures 14 and 15, a system operation example relating to a modification of the first embodiment will be explained, mainly focusing on the differences from the first embodiment. In the first embodiment described above, the case where both the DU and RU are activated in a small station 270S that has been instructed to wake from sleep was explained. In the system operation example relating to a modification of the first embodiment, the case where the timing of the RU's activation differs from the timing of the DU's activation will be explained. Note that the processes from steps S210 to S250, S270 to S310, and S320 to S370 are the same as the processes from steps S10 to S50, S70 to S110, and S120 to S170 in Figures 9 and 10, so their explanation will be omitted.
[0097] In step S260a, the DU is activated in small stations 270S-1 through 270S-N, each of which has received an instruction to wake from sleep. The RU is not activated. Subsequently, the process in step S270 is performed.
[0098] In step S315a, the RU is activated in small stations 270S-1 through 270S-N. The RU activates the transmitter and receiver. Then, in step S320, an SSB search is performed.
[0099] In this embodiment, an example has been described in which a sleep wake-up instruction, operational settings, and SSB settings are transmitted from CU260 to the small station 270S, but it is not limited to this. Two or more of the sleep wake-up instruction, operational settings, and SSB settings may be included in a single message transmitted from CU260 to the small station 270S.
[0100] (2) Second Embodiment Referring to Figures 16 and 17, the second embodiment will be described, primarily focusing on the differences from the first embodiment. In the second embodiment, CU260 transmits transmission frequency information indicating the transmission frequency of PRACH to the second distributed unit via the first distributed unit constituting the PCell to UE100. Macro station 270M is an example of the first distributed unit. Small station 270S is an example of the second distributed unit.
[0101] (2.1) Example of system operation according to the second embodiment Referring to Figures 16 and 17, an example of system operation according to the second embodiment will be described, mainly focusing on the differences from the first embodiment. Note that the processes in steps S410 to S450, S470, S540, S570, and S580 are the same as the processes in steps S10 to S50, S70, S160, S140, and S170 in Figures 9 and 10, and therefore their explanation will be omitted.
[0102] In step S460, both the DU and RU are activated in small stations 270S-1 through 270S-N, each of which has received an instruction to wake from sleep. The RU activates at least the receiver. The RU may also activate the transmitter along with the receiver. However, in order to reduce power consumption, it is preferable that when small station 270S receives an instruction to wake from sleep, only the receiver is activated and the transmitter remains in sleep mode.
[0103] In step S470, small station 270S-1 to small station 270S-N each send a request for operational configuration to CU260. At this point, small station 270S-1 to small station 270S-N each send a message to CU260 indicating that they have started up, along with information on the receivable frequency bands, along with the request.
[0104] In step S480, CU260 transmits operational settings to each small station, from 270S-1 to 270S-N. CU260 includes transmit frequency information in these settings. This transmit frequency information indicates the PRACH transmit frequency requested from UE100. CU260 transmits common transmit frequency information to each of the multiple small stations 270S.
[0105] In step S490, CU260 transmits the system information block (SIB) (e.g., SIB1) for each small station 270S-1 to small station 270S-N to UE100 via macro station 270M. CU260 transmits the transmission frequency information to UE100, including it in the SIB. Therefore, CU260 transmits the transmission frequency information to UE100 via macro station 270M. This transmission frequency information is the same information transmitted to each small station 270S-N from small station 270S-1 in step S480. Thus, the transmission frequency information indicates the transmission frequencies of the PRACH that each small station 270S-N can receive. UE100 receives the SIB containing the transmission frequency information. Therefore, UE100 receives information indicating the transmission frequency of the PRACH from macro station 270M to small station 270S.
[0106] Furthermore, CU260 may include the transmission frequency information in information other than SIB and transmit it to UE100.
[0107] In step S500, UE100 transmits a PRACH to each of the multiple small stations 270S, each of which can receive the PRACH. The small stations 270S receive the PRACH from UE100. Here, small stations 270S-1 through 270S-N each receive the PRACH transmitted from UE100 without the application of a precoder. The transmission frequency of the PRACH is the transmission frequency indicated by the transmission frequency information. Transmitting the PRACH without the application of a precoder (i.e., without pre-recording) means, in other words, that the PRACH is radiated in all directions without the formation of a beam.
[0108] As described above, by having the transmission frequency information indicating the PRACH transmission frequency notified in advance from CU260 to small stations 270S-1 and 270S-N, as many small stations 270S as possible can receive PRACH on the same frequency. This reduces the number of PRACH transmissions by UE100.
[0109] In step S510, small stations 270S-1 and 270S-N each notify CU260 of their PRACH reception results. Therefore, small station 270S also notifies CU260 of its PRACH reception results. The PRACH reception results are indicated by the received power of the PRACH. CU260 receives the PRACH reception results from small stations 270S-1 and 270S-N.
[0110] Here, CU260 determines whether to connect small stations 270S-1 through 270S-N to UE100 based on the reception results. For example, CU260 determines which small station 270S to connect to UE100 based on the magnitude of the PRACH's received power. CU260 determines that the small station 270S with the highest PRACH received power will be connected to UE100.
[0111] As another example, CU260 may determine that it will connect a predetermined number of small stations 270S to UE100 in order of the highest received power. As yet another example, CU260 may determine that it will connect small stations 270S whose received power is above a predetermined threshold to UE100.
[0112] Furthermore, CU260 may determine which small station 270S to connect to UE100 based on machine learning. In this machine learning, a pre-trained model is used that, when received power is input, outputs the ranking of the small stations 270S that should connect to UE100. The trained model is generated in advance and stored in UE100. Any type of machine learning may be used. One example of machine learning is deep learning. When training the trained model to generate the pre-trained model, it is preferable to use methods such as transfer learning. CU260 can determine that it should connect a predetermined number of small stations 270S to UE100, in order of the highest rank output by the trained model.
[0113] The following describes an example where CU260 determines that small station 270S-1 should be connected to UE100 from small station 270S-1 to small station 270S-N, but determines that small station 270S-2 to small station 270S-N should not be connected to UE100.
[0114] In step S520, CU260 activates the small station 270S (small station 270S-1) that it has determined will connect to UE100, and instructs the small stations 270S (from small station 270S-2 to small station 270S-N) that it has determined will not connect to UE100 to go to sleep. Therefore, if CU260 determines, based on the PRACH reception result by small station 270S, that small station 270S will not connect to UE100, it instructs that small station 270S to go to sleep. Small station 270S-1 receives an activation instruction from CU260. Small stations 270S-2 to 270S-N each receive a sleep instruction from CU260.
[0115] In step S530, when small station 270S-1 receives the startup instruction, the RU starts the transmitter. Therefore, both the RU's transmitter and receiver are started. Note that if the transmitter is already started in step S460, the process in step S530 is omitted.
[0116] In step S550, UE100 performs an SSB search. Small station 270S-1, which was not instructed to sleep, emits an SSB beam. Therefore, if small station 270S is not instructed to sleep, it transmits SSB to UE100. The information for small station 270S-1 to emit an SSB beam (transmission period, beam settings, etc.) is pre-configured. UE100 receives SSB from small station 270S-1.
[0117] In step S560, UE100 determines that the cell of small station 270S-1 is the optimal PSCell or SCell and transmits PRACH to small station 270S-1. Small station 270S-1 receives PRACH from UE100.
[0118] As described above, in the system operation example according to the second embodiment, UE100 transmits PRACH in step S500 and step S560, respectively. When transmitting PRACH in step S500, UE100 has not obtained the information necessary for the initial access process to small station 270S (such as the SSB index). Therefore, as the initial access process to small station 270S, PRACH is transmitted again in step S560 along with the SSB search. Note that while the PRACH in step S500 is transmitted without pre-recording as described above, the PRACH in step S560 is transmitted with pre-recording. In other words, in step S560, small station 270S-1 receives a PRACH with the pre-coder applied from UE100, which has received the SSB.
[0119] (3) Third Embodiment Referring to Figures 18 and 19, the third embodiment will be described, primarily focusing on the differences from the second embodiment. In the third embodiment, CU260 requests UE100 to transmit a reference signal to the second distributed unit via the first distributed unit constituting the PCell. Macro station 270M is an example of the first distributed unit. Small station 270S is an example of the second distributed unit.
[0120] (3.1) Example of system operation according to the third embodiment Referring to Figures 18 and 19, an example of system operation according to the third embodiment will be described, mainly focusing on the differences from the second embodiment. Note that the processes from steps S610 to S670 and from steps S720 to S780 are the same as the processes from steps S410 to S470 and from steps S520 to S580 in Figures 16 and 17, and therefore their explanation will be omitted. Also, the process of step S680 is the same as the process of step S80 in Figure 9, and therefore its explanation will be omitted.
[0121] In step S690, CU260 requests UE100 via macro station 270M to transmit SRS signals from small station 270S-1 to small station 270S-N, specifying the SRS frequency. UE100 accepts the request from macro station 270M to transmit SRS signals from small station 270S-1 to small station 270S-N. Macro station 270M may send a message containing this request to UE100 at any time.
[0122] Furthermore, CU260 requests UE100 to transmit SRS to macro station 270M via macro station 270M. UE100 accepts the request from macro station 270M to transmit SRS to macro station 270M. Note that macro station 270M may send a message containing this request to UE100 at any time.
[0123] In step S700, UE100 transmits SRS from small station 270S-1 to small station 270S-N and to macro station 270M. UE100 transmits SRS from small station 270S-1 to small station 270S-N and to macro station 270M simultaneously. UE100 transmits SRS from small station 270S-1 to small station 270S-N at the frequencies specified for each small station. Small stations 270S-1 and 270S-N each receive the SRS from UE100. UE100 transmits SRS to macro station 270M at the frequency specified for macro station 270M. Macro station 270M receives the SRS.
[0124] Here, the request for SRS transmission in step S690 is made before the connection between UE100 and small station 270S is established. Therefore, CU260 requests UE100 to transmit SRS to small station 270S via macro station 270M before the connection establishment between UE100 and small station 270S is performed.
[0125] Furthermore, the SRS transmission in step S700 is performed before the connection between UE100 and small station 270S is established. Therefore, small station 270S is not yet synchronized with UE100, and even if small station 270S receives an SRS, it is not possible to accurately measure the distance between UE100 and small station 270S (i.e., the time difference between when UE100 transmits the SRS and when small station 270S receives it). To address this, UE100 also transmits and receives SRS with macro station 270M, with which a connection has already been established, and shares the SRS transmission time measured during this transmission and reception with CU260, thereby enabling calibration of the SRS reception time at small station 270S.
[0126] In step S710, small stations 270S-1 through 270S-N each notify CU260 of their SRS reception results. Macro station 270M also notifies CU260 of its SRS reception results.
[0127] Here, CU260 determines whether to connect small stations 270S-1 through 270S-N to UE100 based on the received results. For example, CU260 determines which small station 270S to connect to UE100 based on the magnitude of the received SRS power. CU260 performs channel estimation based on the SRS received by each of small stations 270S-1 through 270S-N, and determines that the small station 270S with the largest received SRS power will be connected to UE100.
[0128] As another example, CU260 may determine that it will connect a predetermined number of small stations 270S to UE100 in order of their received power, starting with those with the highest received power. As yet another example, CU260 may determine that it will connect small stations 270S whose received power is above a predetermined threshold to UE100.
[0129] Furthermore, CU260 may determine the small station 270S connected to UE100 based on machine learning, as described in the second embodiment. CU260 may determine that it will connect a predetermined number of small stations 270S to UE100, in order of the highest rank output by the trained model.
[0130] In step S720, if CU260 determines, based on the SRS reception results from small station 270S, that it will not connect to UE100, it will instruct small station 270S to go to sleep. The following describes an example where CU260 determines that small station 270S-1 should be connected to UE100 from small station 270S-1 to small station 270S-N, but determines that small station 270S-2 to small station 270S-N should not be connected to UE100.
[0131] In step S750, small station 270S-1 transmits SSB only in the direction from which UE100 can receive the signal most strongly. Small station 270S-1 determines this direction based on the SRS reception result received in step S700. UE100 receives the SRS from small station 270S-1.
[0132] In step S750, the SSB search is simplified compared to conventional SSB searches, as UE100 only transmits SSB in the direction from which it receives the strongest signal. This is because in step S700, UE100 has already transmitted SRS to small station 270S. The simplification of the SSB search results in reduced power consumption and increased speed.
[0133] (4) Fourth Embodiment Referring to Figures 20 and 21, the fourth embodiment will be described, primarily focusing on the differences from the first embodiment. In the fourth embodiment, UE100 is a user device that performs wireless communication with a master node and a secondary node using dual connectivity in a mobile communication system, and receives first information indicating an adjacent cell from the master node. UE100 selects a secondary node to wake from sleep based on the first information. UE100 transmits second information to the master node indicating the adjacent cell that UE100 wants to wake from sleep. Macro station 270M is an example of a master node. Small station 270S is an example of a secondary node.
[0134] (4.1) Example of system operation according to the fourth embodiment Referring to Figures 20 and 21, an example of system operation according to the fourth embodiment will be described, mainly focusing on the differences from the first embodiment. Note that the processes from steps S810 to S840 and from steps S930 to S950 are the same as the processes from steps S10 to S40, S130, S140, and S170 in Figures 9 and 10, respectively, so their explanation will be omitted. Also, the process in step S920 is the same as the process in step S550 in Figure 17, so its explanation will be omitted.
[0135] In step S850, CU260 notifies UE100 of the first information via macro station 270M. Therefore, CU260 transmits the first information to UE100. The first information indicates the nearby sleep-state small station 270S of UE100. Therefore, the first information is information about a sleep-state secondary node. The nearby sleep-state small stations 270S of UE100 are small station 270S-1 to small station 270S-N. UE100 receives the first information from macro station 270M.
[0136] Here, the transmission of the first information from macro station 270M to UE100 occurs after UE100 has transmitted the radio quality condition request to macro station 270M in step S830. Thus, UE100 receives the first information from macro station 270M after UE100 has requested high-throughput communication.
[0137] In step S860, UE100 selects a small station 270S to be woken from sleep mode from among the candidates. Here, UE100 selects the small station 270S to be woken from sleep mode based on connection history information. In this embodiment, UE100 selects the small station 270S to be woken from sleep mode based on machine learning using UE100's current location and connection history information.
[0138] Connection history information is information that shows the connection history of UE100 over a predetermined period in the past (for example, the most recent month). Connection history information includes, for example, the location and time information of when UE100 previously connected with a small station 270S, the identifier of the small station 270S previously connected, and the communication quality of when UE100 connected with the small station 270S previously connected. The location of when UE100 previously connected with a small station 270S is obtained, for example, based on the Global Positioning System (GPS). The identifier of the small station 270S previously connected is, for example, the cell ID of the cell of that small station 270S.
[0139] Furthermore, the connection history information may include the daily movement patterns of the UE100. These movement patterns are expected to be unique to each day, reflecting the daily behavior of the UE100 user.
[0140] The current position of UE100 can be determined based on, for example, the MDT, Timing Advance, or Proximity Indication mentioned above.
[0141] In machine learning, a learning model is used that, given the current location of the UE100 and connection history information as input, outputs a score for each of the 270S small stations to be woken from sleep mode. The learning model is pre-generated and stored in the UE100. Any type of machine learning may be used. One example of machine learning is deep learning. When training the learning model to generate the pre-trained model, it is preferable to use methods such as transfer learning.
[0142] The UE100 generates second-order information by assigning higher rankings to the small stations 270S that have higher scores output by the learning model, in order of priority, to be woken from sleep mode. This second-order information indicates which small stations 270S the UE100 wants to wake from sleep mode based on their ranking.
[0143] In step S870, UE100 transmits second information to CU260 via macro station 270M, indicating the small station 270S that UE100 wants to wake from sleep. Therefore, UE100 transmits second information to macro station 270M, indicating the small station 270S that UE100 wants to wake from sleep. CU260 receives second information from UE100 via macro station 270M.
[0144] In step S880, CU260 instructs small station 270S to wake from sleep. CU260 instructs small station 270S indicated by the second information to wake from sleep. CU260 determines whether it is possible to start up small station 270S in order from the highest-ranking station indicated by the second information. If CU260 determines that it is possible to start up a small station 270S of a certain rank, it stops the process of determining that rank for subsequent ranks. Note that CU260 has previously obtained information indicating whether it is possible to start up small station 270S. CU260 instructs small station 270S that it has determined is possible to wake from sleep.
[0145] As described above, when macro station 27 receives the second information from UE100, it transmits it to CU260 via macro station 270M, and CU260 instructs small station 270S to wake up from sleep. Therefore, when macro station 270M receives the second information, it starts up small station 270S.
[0146] The following describes an example where CU260 determines that small station 270S-1 should be connected to UE100 from small station 270S-1 to small station 270S-N, but determines that small station 270S-2 to small station 270S-N should not be connected to UE100.
[0147] In step S880, CU260 instructs small station 270S-1 to wake from sleep. Therefore, CU260 wakes the adjacent cell from sleep based on the second information received from UE100. Small station 270S-1 receives the instruction to wake from sleep from CU260.
[0148] In step S890, when small station 270S-1 receives a command to wake from sleep, both the DU and RU are activated. The RU activates the transmitter and receiver.
[0149] In step S900, small station 270S-1 sends a request for operational configuration to CU260. Small station 270S-1 sends this request, for example, in an F1 SETUP REQUEST message.
[0150] In step S910, CU260 transmits operational settings to small station 270S-1. CU260 transmits these settings, for example, in an F1 SETUP RESPONSE message.
[0151] In the fourth embodiment, an example of how machine learning is used in the process of selecting the small station 270S to be woken from sleep was described, but the invention is not limited to this. In this process, a table may be used instead of machine learning. For example, the table may be one in which a pair of the current location of the UE100 and connection history information is associated with a pair of scores for each of the small stations 270S to be woken from sleep.
[0152] In the second, third, and fourth embodiments described above, an example was given in which a sleep wake-up instruction and operational settings are transmitted from CU260 to the small station 270S, but the invention is not limited to this example. The sleep wake-up instruction and operational settings may be included in a single message transmitted from CU260 to the small station 270S.
[0153] In the system operation examples of each embodiment described above, an example was explained in which the macro station 270M is included in MN200M and the small station 270S is included in SN200S. In other words, an example was explained in which the macro station 270M and the small station 270S belong to different cell groups, but it is not limited to this. The macro station 270M and the small station 270S may belong to the same cell group. For example, the macro station 270M and the small station 270S may be included in MN200M. The system operation examples of each embodiment described above may be implemented in the case in which the macro station 270M and the small station 270S belong to the same cell group.
[0154] A program may be provided that causes a computer (UE100, node200) to perform the operations according to the above embodiment. 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-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM. Furthermore, the circuits that perform each process performed by UE100 or node200 may be integrated, and at least a part of UE100 or node200 may be configured as a semiconductor integrated circuit (chipset, system-on-a-chip (SoC)).
[0155] In the above embodiment, an example was described in which node 200 is an NR base station (gNB), but node 200 may also be an LTE base station (eNB) or a 6G base station. Furthermore, node 200 may also be a relay node such as an IAB (Integrated Access and Backhaul) node. Node 200 may also be a DU of an IAB node. Additionally, UE100 may be an MT (Mobile Termination) of an IAB node.
[0156] Furthermore, the term "node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU (Radio Unit)). A node may also consist of a combination of at least a part of the core network device and at least a part of a base station.
[0157] Although one embodiment of this invention has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the spirit of this invention. [Explanation of symbols]
[0158] 1…Network 10...RAN 20…CN 100…UE 110... Receiver 120...Transmitter 130... Control Unit 140... Wireless Communication Department 200...nodes 210...Transmitter 220... Receiver 230... Control Unit 240...NW Communications Department 250... Wireless Communication Department 300…CN device
Claims
1. A user device that performs wireless communication with a master node and a secondary node using dual connectivity in a mobile communication system, The first information indicating an adjacent cell is received from the master node, Select the secondary node to wake from sleep based on the first information, The user device transmits second information to the master node indicating the adjacent cell it wants to wake from sleep. User device.
2. The first information is received from the master node after the user device requests high-throughput communication. The user device according to claim 1.
3. The first information is information about the secondary node that is in a sleep state. The user device according to claim 1.
4. The secondary node to be woken from sleep is selected based on the connection history information. The user device according to claim 1.
5. The aforementioned connection history information is, The location and time information when the user device previously connected to the secondary node, The identifier of the secondary node that was previously connected, Includes the communication quality when the secondary node and the user device were connected in the past. The user device according to claim 4.
6. When the master node receives the second information, it starts the secondary node. The user device according to claim 1.
7. A node operating in a mobile communication system where user equipment performs wireless communication using dual connectivity, The aforementioned node is The first information indicating adjacent cells is transmitted to the user device. The user device receives second information from the user device indicating an adjacent cell that it wants to wake from sleep mode. Based on the received second information, wake the adjacent cell from sleep. node.
8. A communication method used in a user device that performs wireless communication with a master node and a secondary node using dual connectivity in a mobile communication system, The steps include receiving first information indicating adjacent cells from the master node, A step of selecting a secondary node to wake from sleep based on the first information, The user device transmits second information to the master node indicating an adjacent cell that it wants to wake from sleep. Communication method.
9. A communication method used in a node that performs wireless communication with user equipment using dual connectivity in a mobile communication system, A step of transmitting first information indicating adjacent cells to the user device, The user device receives second information from the user device indicating an adjacent cell that it wants to wake from sleep mode. The steps include: waking an adjacent cell from sleep based on the received second information; A communication method that includes [something].