Network node, user device, and communication method

Abstract

A network node according to a first aspect manages a cell in a mobile communication system, and comprises: a transmission unit that transmits, by beamforming, a synchronization signal block used in a cell search performed by a user device; and a control unit that performs beam sweeping for switching a transmission beam direction of the synchronization signal block at predetermined time intervals. The control unit controls the transmission unit to simultaneously transmit N (N: an integer of 2 or more) synchronization signal blocks in a band of the cell at different frequencies.

Description

Network node, user equipment, and communication method

[0001] The present disclosure relates to a network node, a user equipment, and a communication method for use in a mobile communication system.

[0002] The technical specifications of 5G (5th Generation) / NR (New Radio) of the 3rd Generation Partnership Project (3GPP (registered trademark; the same applies hereinafter)) use radio waves in a higher frequency band for wireless communication than 4G (4th Generation) / LTE (Long Term Evolution). Because propagation loss increases in high frequency bands, beamforming, which narrows the direction in which radio waves are transmitted, is used for wireless communication, and the propagation loss is compensated for by beam gain.

[0003] A network node (e.g., a base station) managing a cell transmits synchronization signal blocks (SSBs: Synchronization Signal / Physical Broadcast Channel Blocks) by beamforming, which are used for cell search by a user equipment. Cell search is a procedure in which a user equipment obtains time and frequency synchronization with a cell and detects the cell ID of the cell. The user equipment performs cell search based on a primary synchronization signal, a secondary synchronization signal, and a demodulation reference signal (DMRS) of the PBCH in the SSBs.

[0004] In order to transmit SSBs throughout the entire coverage area of ​​a cell, a network node performs beam sweeping, which switches the transmission beam direction of the SSBs (also referred to as a "beamforming pattern") at predetermined time intervals. For example, the network node transmits SS bursts (also referred to as "SS burst sets" or "synchronization signal bursts") consisting of multiple SSBs arranged in the time direction at 20-ms intervals. Here, the network node uses beam sweeping to time-divisionally transmit each SSB within the SS burst in a different transmission beam direction. This allows the SSBs to be distributed throughout the entire coverage area of ​​the cell within the SS burst, even when transmitting the SSBs using beamforming. Note that the SS burst is specified to be set within a predetermined time length (specifically, the time of a half frame).

[0005] The higher the frequency band, the more beamforming that can form sharper beams is used, and the number of SSBs in an SS burst tends to increase. For example, in FR (Frequency Range) 1, which corresponds to the Sub6 band, a maximum of eight SSBs (i.e., a maximum of eight SSB beamforming patterns) can be used in an SS burst, and in FR2, which corresponds to the millimeter wave band, a maximum of 64 SSBs (i.e., a maximum of 64 SSB beamforming patterns) can be used in an SS burst.

[0006] 3GPP Technical Specification: 3GPP TS 38.300 V17.6.0 (2023-09)

[0007] For 6G (6th Generation), the use of the sub-terahertz band (e.g., a frequency range of 90 GHz to 300 GHz), which is a frequency band higher than the millimeter wave band, is being primarily considered. In the sub-terahertz band, it is expected that the number of SSBs in an SS burst will further increase. Therefore, there is a concern that the time required for a network node to distribute SSBs throughout a cell, i.e., the time required for beam sweeping, will increase. Similarly, there is a concern that the time required for a user device to perform a cell search will also increase.

[0008] The present disclosure provides a network node, a user device, and a communication method that can suppress an increase in the time required for beam sweeping and cell search even when a higher frequency band is used in a mobile communication system.

[0009] A network node according to a first aspect is a network node that manages cells in a mobile communication system, and includes: a transmitter that transmits synchronization signal blocks used in cell search performed by user equipment by beamforming; and a controller that performs beam sweeping to switch the transmission beam direction of the synchronization signal blocks at predetermined time intervals. The controller controls the transmitter to simultaneously transmit N (N: an integer of 2 or greater) synchronization signal blocks at different frequencies within the band of the cell.

[0010] A user equipment according to a second aspect is a user equipment that performs wireless communication with a network node that manages a cell in a mobile communication system, and includes: a receiver that receives synchronization signal blocks that are transmitted from the network node by beamforming and to which beam sweeping that switches the transmission beam direction at predetermined time intervals is applied; and a controller that performs cell search based on the synchronization signal blocks. The receiver receives at least one of N (N: an integer of 2 or greater) synchronization signal blocks that are simultaneously transmitted at different frequencies within the band of the cell.

[0011] A communication method according to a third aspect is a communication method used in a network node that manages a cell in a mobile communication system, the method comprising the steps of: transmitting a synchronization signal block used in a cell search performed by a user equipment by beamforming; and performing beam sweeping to switch the transmission beam direction of the synchronization signal block at predetermined time intervals. The step of transmitting the synchronization signal block includes the step of simultaneously transmitting N (N: an integer of 2 or greater) synchronization signal blocks at different frequencies within the band of the cell.

[0012] A communication method according to a fourth aspect is a communication method used by a user equipment that performs wireless communication with a network node that manages a cell in a mobile communication system, the method comprising the steps of: receiving a synchronization signal block that is transmitted from the network node by beamforming and to which beam sweeping that switches a transmission beam direction at predetermined time intervals is applied; and performing a cell search based on the synchronization signal block. The step of receiving the synchronization signal block includes the step of receiving at least one of N (N: an integer greater than or equal to 2) synchronization signal blocks that are simultaneously transmitted at different frequencies within a band of the cell.

[0013] 1 is a diagram illustrating an example of the configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack of a radio interface of a U-plane that handles data. FIG. 3 is a diagram illustrating an example of the configuration of a protocol stack of a radio interface of a C-plane that handles signaling (control signals). FIG. 4 is a diagram for explaining an overview of SSB, beam sweeping, and cell search according to an embodiment. FIG. 5 is a diagram for explaining an overview of SSB, beam sweeping, and cell search according to an embodiment. FIG. 6 is a diagram illustrating an example of the configuration of a base station (network node) according to an embodiment. FIG. 7 is a diagram for explaining a comparative example. FIG. 8 is a diagram illustrating an example of an SSB transmission operation according to an embodiment. FIG. 9 is a diagram illustrating another example of an SSB transmission operation according to an embodiment. FIG. 10 is a diagram for explaining OffsetToPointA and Kssb (ssb-SubcarrierOffset). FIG. 11 is a diagram illustrating an example of the configuration of a UE (user equipment) according to an embodiment. FIG. 12 is a diagram illustrating an example of the operation of a base station (network node) according to an embodiment.

[0014] 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 parts are denoted by the same or similar reference numerals.

[0015] (1) System Configuration Example Fig. 1 is a diagram showing a configuration example of a mobile communication system according to this embodiment. The mobile communication system according to this embodiment is a system conforming to the 3GPP standard. For example, the mobile communication system according to this embodiment may be a fifth-generation (5G) system or a sixth-generation (6G) system.

[0016] The mobile communication system includes a network (NW) 1 and a user equipment (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, and may be, for example, 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 provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0017] NW1 includes a radio access network (RAN) 10 and a core network (CN) 20. When the mobile communication system is a 5th generation system (5GS), the RAN 10 is referred to as a Next Generation Radio Access Network (NG-RAN), and the CN 20 is referred to as a 5G Core Network (5GC).

[0018] The RAN 10 includes a plurality of base stations 200 (base stations 200a to 200c in the illustrated example). The base stations 200 are connected to each other via an inter-base station interface. The base station 200 is an example of a network node. The base station 200 may be configured (i.e., functionally divided) with a CU (Central Unit) and a DU (Distributed Unit), and the two units may be connected via a fronthaul interface. When the mobile communication system is 5GS, the base station 200 is referred to as a gNB, the inter-base station interface is referred to as an Xn interface, and the fronthaul interface is referred to as an F1 interface.

[0019] Each base station 200 manages one or more cells. The base station 200 performs wireless communication with the UE 100 that has established a connection with the base station 200's cell. Each base station 200 has a radio resource management (RRM) function, a user data (also simply referred to as "data") routing function, a measurement control function for mobility control and scheduling, and the like. Note that the term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency. One downlink component carrier and one uplink component carrier may be associated with one cell. The bandwidth corresponding to one cell (system bandwidth) may be divided into multiple bandwidth parts (BWP: Bandwidth Parts).

[0020] The CN 20 includes a CN device 300. The 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 the UE 100. The C-plane device communicates with the UE 100 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 referred to as an AMF (Access and Mobility Management Function), the U-plane device is referred to as a UPF (User Plane Function), and the interface between the base station 200 and the CN device 300 is referred to as an NG interface.

[0021] FIG. 2 is a diagram showing an example of the configuration of a protocol stack of a U-plane radio interface that handles data.

[0022] The U-plane radio interface protocol includes, for example, a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0023] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the base station 200 via a physical channel. The PHY layer of the UE 100 receives downlink control information (DCI) transmitted from the base station 200 on a physical downlink control channel (PDCCH). Specifically, the UE 100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from the base station 200 has CRC parity bits scrambled by the RNTI added thereto.

[0024] 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 UE 100 and the MAC layer of base station 200 via a transport channel. The MAC layer of base station 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to UE 100.

[0025] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and the PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the base station 200 via logical channels.

[0026] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0027] The SDAP layer maps IP flows, which are units for QoS control by the CN 20, to radio bearers, which are units for QoS control by an AS (Access Stratum). Note that if the CN 30 controls QoS in the same units as the RAN 20 (i.e., if QoS control is performed in bearer units rather than IP flow units, and one-to-one mapping with radio bearers is possible), the SRAP layer may not be necessary.

[0028] FIG. 3 is a diagram showing an example of the configuration of a protocol stack of a C-plane radio interface that handles signaling (control signals).

[0029] The protocol stack of the C-plane radio interface includes, for example, an RRC (Radio Resource Control) layer and an NAS (Non-Access Stratum) layer instead of the SDAP layer shown in FIG.

[0030] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of base station 200. The RRC layer controls logical channels, transport channels, and physical channels in accordance with the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of base station 200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of base station 200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of base station 200 is suspended, UE100 is in an RRC inactive state.

[0031] The NAS layer (also simply referred to as "NAS") located above the RRC layer performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the CN device 300. Note that the UE 100 also has an application layer in addition to the radio interface protocol. The layer below the NAS layer is referred to as the AS layer (also simply referred to as "AS").

[0032] (2) Overview of SSB, Beam Sweeping, and Cell Search FIGS. 4 and 5 are diagrams for explaining an overview of SSB, beam sweeping, and cell search according to this embodiment.

[0033] As shown in FIG. 4, in the frame structure used in 5G / NR wireless communication, one frame (radio frame) is 10 ms in the time axis direction. A frame is composed of 10 subframes, each of which is 1 ms. Each subframe is composed of a number of slots according to the waveform configuration (also referred to as "numerology"), such as the subcarrier spacing. Specifically, the length of the slot in the time axis direction becomes shorter as the subcarrier spacing increases. The number of symbols in one slot is 14 in the case of a normal CP (Cyclic Prefix). Meanwhile, one resource block (RB) is composed of 12 subcarriers in the frequency axis direction. Furthermore, one symbol and one subcarrier constitute one resource element (RE).

[0034] The base station 200 that manages the cell transmits SSBs (SS / PBCH blocks) used by the UE 100 for cell search. Each SSB consists of four symbols in the time axis direction and 240 consecutive subcarriers (i.e., 20 RBs) in the frequency axis direction. These subcarriers are numbered in ascending order from 0 to 239 within the SSB, from the lowest frequency side to the highest frequency side. The lowest frequency subcarrier within an SSB is also referred to as subcarrier 0. Note that each of the PSS and SSS consists of one symbol and 127 subcarriers. The PBCH consists of three symbols and 240 subcarriers.

[0035] Each SSB includes a synchronization signal (SS) and a physical broadcast channel (PBCH). The SS includes a primary synchronization signal (PSS) and a secondary synchronization signal (SSS). The PSS and SSS are used for synchronization at least in the time axis direction. The combination of the PSS and SSS signal sequences indicates the cell ID (PCI: Physical Cell ID) of the transmitting cell. The PBCH includes a master information block (MIB) and a demodulation reference signal (DMRS). The MIB includes parameters for decoding the system information block type 1 (SIB1). The DMRS is a reference signal for decoding the PBCH. Note that SIB1 is also referred to as the remaining minimum system information (RMSI). The SSB associated with SIB1 (RMSI) is referred to as a cell-defined SSB (CD-SSB). In the following, SSB refers to a CD-SSB.

[0036] The SSBs are arranged continuously in the time direction at specific frequencies within the cell band. Specifically, in the current 3GPP technical specifications, the SSBs are arranged at a unique frequency predetermined by the base station 200, and the SSBs are repeatedly transmitted in the time direction. The positions of the SSBs on the frequency axis can be notified from the base station 200 to the UE 100 by RRC signaling.

[0037] The base station 200 periodically transmits SS bursts (also referred to as "SS burst sets" or "synchronization signal bursts") consisting of multiple SSBs arranged in the time direction. The transmission period of the SS bursts can be selected from 5 ms, 10 ms, 20 ms, 40 ms, 80 ms, and 160 ms, with 20 ms being the most common. The maximum number of SSBs in one SS burst, i.e., the maximum number of consecutive SSBs, is 8 for FR1, which corresponds to the Sub6 band, and 64 for FR2, which corresponds to the millimeter wave band. In the example of FIG. 4, the transmission period of the SS bursts is 20 ms, and the number of SSBs in an SS burst is 8. Note that SS bursts are specified to be set within the time of a half frame (5 ms). The time positions at which SSBs can be placed within a half frame are determined according to the subcarrier spacing. On the other hand, the transmission period of the SS burst (i.e., the periodicity of the half frame in which the SSB is transmitted) is set by NW1 (base station 200).

[0038] Although the example of Fig. 4 shows a case where all SSBs in an SS burst are transmitted, base station 200 does not necessarily need to transmit all SSBs in an SS burst. Base station 200 can selectively transmit only some of the SSBs in an SS burst according to the requirements of NW1. Furthermore, base station 200 can notify UE 100 by RRC signaling which SSBs are to be transmitted and which are not to be transmitted in an SS burst. Specifically, this transmission pattern is notified to UE 100 by an RRC information element (IE) called ssb-PositionInBurst.

[0039] Base station 200 assigns an SSB index (SSB index), which is an identifier of the SSB, to each SSB in an SS burst. In the example of FIG. 4, "#1" to "#8" represent the SSB index. This number is reset to 1 in the next SS burst. The SSB index may be a unique number that starts from 0 and increments by 1. If the SSB index starts from 0, it is reset to 0 in the next SS burst. Base station 200 notifies UE 100 of the SSB index via the PBCH in the SSB. UE 100 that receives an SSB can identify the SSB index of the SSB based on the PBCH in the received SSB.

[0040] As shown in FIG. 5 , in order to transmit SSBs throughout the entire coverage area of ​​the cell, base station 200 performs beam sweeping, which switches the transmission beam direction of the SSBs (also referred to as a "beamforming pattern (BF pattern)") at predetermined time intervals within the period of each SS burst (SS burst period). That is, base station 200 uses beam sweeping to time-division transmit each SSB within an SS burst in a different transmission beam direction. Therefore, during a half frame, different SSBs are transmitted in different spatial directions (i.e., different transmission beam directions) across the cell coverage area. This allows SSBs to be transmitted throughout the entire coverage area of ​​the cell (cell coverage) within an SS burst, even when beamforming is used to transmit SSBs.

[0041] UE100 performs cell search based on the SSB (specifically, the PSS, SSS, and DMRS in the SSB). Cell search is a procedure in which UE100 obtains time and frequency synchronization with a cell and detects the cell ID of the cell. UE100 performs SSB scanning (cell search) on a synchronization raster, which is a position on the frequency axis where SSBs can be arranged. UE100 measures the reception quality of each received SSB and identifies an SSB index of an SSB whose reception quality satisfies a predetermined condition, thereby identifying an appropriate beam. Here, the reception quality may be RSRP (Reference Signal Received Power) in the SSB. The predetermined condition may be a condition that the reception quality exceeds a threshold. The predetermined condition may be a condition that the reception quality is the highest among SSBs received within a predetermined period (e.g., an SS burst period). In the example of FIG. 5, since the reception quality of SSB#2 is the highest, UE 100 can identify SSB#2 as the SSB whose reception quality satisfies a predetermined condition.

[0042] UE100 performs random access (RA) for initial access to NW1 (base station 200). Specifically, UE100 transmits an RA preamble to base station 200 to perform RA. RA occasions, which are timings at which RA preambles can be transmitted, are prepared as many times as the number of transmission beams of base station 200 (i.e., the number of SSBs in an SS burst). UE100 transmits the RA preamble to base station 200 in the RA occasion corresponding to an SSB (SSB Index) whose reception quality satisfies a predetermined condition. Having received the RA preamble, base station 200 can determine the transmission beam preferred for UE100 (i.e., the direction in which UE100 is located) based on the correspondence between the beam (SSB Index) and the RA occasion.

[0043] The RA occasion is notified to UE 100 in system information provided by base station 200. Specifically, base station 200 notifies UE 100 of the time and frequency resources of the RA occasion. There is a one-to-one relationship between SSB and RA occasion. When base station 200 directs a transmission beam in a certain direction and receives an RA occasion corresponding to the SSB, it receives the SSB using a reception beam directed in the same direction as the transmission beam.

[0044] In the mobile communication system 1, beam sweeping and cell search are performed in this manner. Here, the higher the frequency band, the more beamforming is utilized, which can form sharper beams. In 6G, the use of the sub-terahertz band (e.g., a frequency range of 90 GHz to 300 GHz) is mainly being considered, but it is expected that the number of SSBs in an SS burst will further increase in the sub-terahertz band. Therefore, there is a concern that the time required for the base station 200 to distribute SSBs throughout the entire cell, i.e., the time required for beam sweeping, will increase. Similarly, there is a concern that the time required for the UE 100 to perform cell search will also increase.

[0045] (3) Configuration Example of Base Station Fig. 6 is a diagram showing a configuration example of a base station 200 (network node) according to this embodiment. The base station 200 according to this embodiment may be configured to perform wireless communication in the sub-terahertz band.

[0046] The base station 200 includes a transmitting unit 210, a receiving unit 220, a control unit 230, and a NW communication unit 240. The transmitting unit 210 and the receiving unit 220 configure a wireless communication unit 250 that performs wireless communication with the UE 100.

[0047] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a 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 receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (reception signal) and outputs it to the control unit 230.

[0048] To compensate for propagation loss at high frequencies, the wireless communication unit 250 must perform beamforming, which imparts directivity to the antenna and narrows the direction in which radio waves are transmitted. In order to control the antenna's directivity, digital beamforming requires the same number of antenna weights in the digital domain as the number of antenna elements. These antenna weights are weights for controlling amplitude and phase. However, controlling them in the digital domain results in a large digital circuit. For this reason, it is common to use phase shifters, which are antenna weights that can control only the phase in the analog domain. Digital domain antenna weights are realized in the frequency domain when using an OFDM modulation scheme, i.e., before the inverse fast Fourier transform (IFFT) during transmission. During reception, they are realized after the fast Fourier transform (FFT). Therefore, when digital domain antenna weights are realized in the frequency domain, beams can be directed in different directions using different frequency resources even at the same time. On the other hand, antenna weights realized in the analog domain always control the antenna weights in the time domain, so beams can only be directed in the same direction across all frequency domains at the same time. Furthermore, while one antenna panel typically cannot form beams in different directions using different frequencies at the same time, two antenna panels can form beams in different directions even at the same time. Therefore, in this embodiment, the wireless communication unit 250 may have N antenna panels (N: an integer of 2 or greater).

[0049] The control unit 230 performs various controls and processes in the base station 200. The operations of the base station 200 described above and below may be operations under the control of 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 in the 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.

[0050] The NW communication unit 240 is connected to adjacent base stations via an inter-base station interface, and is also connected to the CN device 300 via a base station-CN interface.

[0051] The base station 200 configured as described above manages cells in a mobile communication system. The transmitter 210 transmits SSBs used in cell search performed by the UE 100 by beamforming. The controller 230 performs beam sweeping, which switches the transmission beam direction of the SSBs (i.e., BF pattern) at predetermined time intervals. FIG. 7 is a diagram showing an example of beam sweeping. The base station 200 holds multiple BF patterns. The base station 200 transmits SSBs in sequence while switching the BF pattern. In the example of FIG. 7, the base station 200 transmits SSB #1 with a certain BF pattern during the SS burst period in a half frame, and then transmits SSB #2 with a different BF pattern. For example, a BF pattern 30° to the left as viewed from the base station 200 is transmitted in SSB #1, and then a BF pattern 10° to the left as viewed from the base station 200 is transmitted in SSB #2. In this way, BF patterns and SSBs are transmitted in a one-to-one correspondence. The positions where SSBs can be arranged in the time axis direction within the SS burst period may be determined according to the subcarrier spacing, i.e., the predetermined time interval for switching BF patterns may be determined according to the subcarrier spacing.

[0052] In this embodiment, the control unit 230 controls the transmission unit 210 to simultaneously transmit N SSBs (N: an integer of 2 or greater) at different frequencies within the band of the cell (home cell). In particular, the control unit 230 controls the transmission unit 210 to simultaneously transmit N SSBs at different frequencies and in different transmission beam directions (different BF patterns) within the band of the cell. In the sub-terahertz band, it is expected that the number of SSBs in an SS burst will further increase. However, by simultaneously transmitting N SSBs (N: an integer of 2 or greater) at different frequencies (i.e., N frequencies) within the band of the home cell, the time required for beam sweeping can be reduced to 1 / N compared to transmitting SSBs at a single frequency within the band of the home cell.

[0053] Here, as a comparative example, a case where multiple SSBs are transmitted at the same frequency is assumed. FIG. 8 is a diagram for explaining the comparative example. In the comparative example shown in FIG. 8, multiple BF patterns are simultaneously applied to one SSB within the band of the own cell, thereby attempting to complete beam sweeping accordingly more quickly. However, when signals (SSBs in this case) at the same time and frequency are transmitted using multiple BF patterns, the BF patterns interfere with each other in a complex manner, resulting in a distorted beam that differs from the originally designed BF pattern, and resulting in unexpected beam sweeping.

[0054] In contrast, the base station 200 according to this embodiment simultaneously transmits N SSBs at different frequencies (N frequencies) within the band of its own cell, thereby multiplexing different SSBs using frequency division and suppressing interference between BF patterns. Therefore, beam sweeping is possible using the originally designed BF pattern. FIG. 9 is a diagram showing an example of SSB transmission operation according to this embodiment. While an example where N=2 will be mainly described below, N may be an integer equal to or greater than 3. In the example shown in FIG. 9 , the base station 200 first transmits SSB #1 using a first BF pattern and SSB #33 using a second BF pattern that is spatially consecutive to the first BF pattern. Here, the transmission frequencies of SSB #1 and SSB #33 are different from each other. Next, the base station 200 transmits SSB #2 using a third BF pattern that is spatially consecutive to the second BF pattern and SSB #34 using a fourth BF pattern that is spatially consecutive to the third BF pattern. Here, the transmission frequency of SSB #2 and the transmission frequency of SSB #34 are different from each other. Specifically, the transmission frequency of SSB #2 is the same as the transmission frequency of SSB #1, and the transmission frequency of SSB #34 is the same as the transmission frequency of SSB #33.

[0055] FIG. 10 is a diagram showing an example of SSB transmission operation according to this embodiment. The transmitter 210 of the base station 200 according to this embodiment transmits a first SSB group at a first frequency within the cell band during a periodically occurring SS burst period, and transmits a second SSB group at a second frequency within the cell band. In the example shown in FIG. 10 , the first SSB group consists of SSB #1 through SSB #32, and the second SSB group consists of SSB #33 through SSB #64. Therefore, a total of 64 SSBs are transmitted within one SS burst period. By transmitting two SSB groups at two frequencies in parallel, the time required for SSB transmission can be reduced by half compared to transmitting 64 SSBs at one frequency.

[0056] The control unit 230 of the base station 200 according to this embodiment controls beam sweeping so that, within each SS burst period, the first SSB group covers a first portion of the cell's coverage area, and the second SSB group covers a second portion of the coverage area. That is, the control unit 230 differentiates the area covered by the first SSB group from the area covered by the second SSB group within the coverage area of ​​the base station's own cell. This allows for efficient beam sweeping.

[0057] In the example shown in FIG. 10 , the control unit 230 assigns an SSB index to each SSB so that the SSB index of the first SSB group (SSB #1 to SSB #32) does not overlap with the SSB index of the second SSB group. This makes it possible to uniquely identify SSBs within an SS burst period by the SSB index. Although "#1" to "#64" represent the SSB indexes, the SSB index may be a unique number that starts from 0 and increases by 1 over time. This number is reset to 0 in the next SS burst. The base station 200 notifies the UE 100 of the SSB index via the PBCH in the SSB. The UE 100 that receives an SSB can identify the SSB index of the received SSB based on the PBCH in the received SSB.

[0058] The control unit 230 may assign different frequency indexes (ssb-freqIdx) to the SSBs of the first SSB group and the SSBs of the second SSB group. The ssb-freqIdx may be a unique number that starts from 0 and increases by one from the lower frequency side to the higher frequency side. The base station 200 may notify the UE 100 of the ssb-freqIdx via the PBCH in the SSB. The UE 100 that receives the SSB can identify the ssb-freqIdx of the received SSB (i.e., the frequency at which the received SSB is counted from the lowest) based on the PBCH in the received SSB.

[0059] Alternatively, the control unit 230 may assign identifiers to the SSBs so that the identifiers of the SSBs in the first SSB group and the identifiers of the SSBs in the second SSB group at least partially overlap. In this case, the control unit 230 assigns different frequency indexes (ssb-freqIdx) to the SSBs in the first SSB group and the SSBs in the second SSB group. FIG. 11 is a diagram showing another example of the SSB transmission operation according to this embodiment. In the example shown in FIG. 11, the first SSB group consists of SSB #1 through SSB #32 with ssb-freqIdx = 0, and the second SSB group consists of SSB #1 through SSB #32 with ssb-freqIdx = 1. In other words, the first SSB group and the second SSB group share the same SSB Index. Base station 200 notifies UE 100 of the SSB Index and ssb-freqIdx by the PBCH in the SSB. UE 100 that has received the SSB can identify the SSB Index and ssb-freqIdx of the received SSB based on the PBCH in the received SSB.

[0060] The transmitter 210 of the base station 200 according to this embodiment transmits N pieces of configuration information indicating parameters of N SSBs to be simultaneously transmitted at different frequencies. For example, the controller 230 generates the N pieces of configuration information, and the transmitter 210 transmits the N pieces of configuration information to the UE 100 via the PBCH (MIB), SIB, or RRC message (e.g., an RRC Reconfiguration message).

[0061] Each of the N pieces of setting information may be at least one piece of information (setting parameters) from the following 1) to 3).

[0062] 1) OffsetToPointA OffsetToPointA is information indicating, in resource block units, the frequency offset between the subcarrier on the lowest frequency side of the corresponding SSB (subcarrier 0) and a reference point (referred to as "Point A") on the resource block grid, as shown in Fig. 12. Point A indicates the reference position on the frequency axis.

[0063] Base station 200 may notify (set) N OffsetToPointA in SIB1 to UE 100. For example, base station 200 includes, in SIB1 broadcast in its own cell, OffsetToPointA for each of N SSBs to be simultaneously transmitted in different frequencies within the cell.

[0064] SIB1 includes a FrequencyInfoDL-SIB, which is an IE that provides basic parameters for a downlink carrier and transmission on the downlink carrier. In this embodiment, the FrequencyInfoDL-SIB may include N OffsetToPointAs. In the FrequencyInfoDL-SIB, each of the N OffsetToPointAs may be associated with an ssb-freqIdx. For example, the N OffsetToPointAs may be provided in a list format, and the order of the OffsetToPointAs in the list (i.e., the position of the entry) may indicate the ssb-freqIdx. Alternatively, the FrequencyInfoDL-SIB may include N sets of OffsetToPointAs and ssb-freqIdx.

[0065] 2) Kssb (ssb-SubcarrierOffset) Kssb (ssb-SubcarrierOffset) is, as shown in FIG. 12, information indicating the frequency offset between the subcarrier (subcarrier 0) on the lowest frequency side of the corresponding SSB and the boundary on the lower frequency side of the resource block to which the subcarrier (subcarrier 0) belongs, in subcarrier units. Therefore, the UE 100 can obtain the reference point (Point A) of the resource block grid by subtracting the sum of Kssb (ssb-SubcarrierOffset) and OffsetToPointA from subcarrier 0.

[0066] Base station 200 may notify (set) N Kssb (ssb-SubcarrierOffset) to UE 100. For example, base station 200 includes, in an MIB broadcast in its own cell, Kssb (ssb-SubcarrierOffset) of each of N SSBs simultaneously transmitted at different frequencies within the cell.

[0067] Thus, in this embodiment, the MIB may include N OffsetToPointAs. In the MIB, each of the N Kssb(ssb-SubcarrierOffset) may be associated with an ssb-freqIdx. For example, the N Kssb(ssb-SubcarrierOffset) may be provided in list form, and the order of the Kssb(ssb-SubcarrierOffset) in the list (i.e., the position of the entry) may indicate the ssb-freqIdx. Alternatively, the MIB may include N sets of Kssb(ssb-SubcarrierOffset) and ssb-freqIdx.

[0068] 3) absoluteFrequencySSB absoluteFrequencySSB is information indicating the frequency of the corresponding SSB (ARFCN: Absolute Radio-Frequency Channel Number). The frequency indicated by absoluteFrequencySSB may be the position of resource element RE=#0 of resource block RB#10 of the SSB.

[0069] For example, when configuring a secondary cell (SCell) for the UE 100, the base station 200 notifies (configures) N absoluteFrequency SSBs for the secondary cell to the UE 100 by an RRC Reconfiguration message. In this manner, in this embodiment, the RRC Reconfiguration message may include N absoluteFrequency SSBs. In the RRC Reconfiguration message, each of the N absoluteFrequency SSBs may be associated with an ssb-freqIdx. For example, N absoluteFrequencySSBs may be provided in a list format, and the order of the absoluteFrequencySSBs in the list (i.e., the position of the entry) may indicate the ssb-freqIdx. Alternatively, the RRC Reconfiguration message may include N sets of absoluteFrequencySSBs and ssb-freqIdx.

[0070] (4) Example of Configuration of User Equipment Fig. 13 is a diagram showing an example of the configuration of the UE 100 (user equipment) according to this embodiment. The UE 100 according to this embodiment may be configured to perform wireless communication in the sub-terahertz band.

[0071] The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 configure a wireless communication unit 140 that performs wireless communication with the base station 200.

[0072] The receiving unit 110 performs various receptions under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a 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 transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmitted signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0073] The control unit 130 performs various controls and processes in the UE 100. The operations of the UE 100 described above and below may be operations 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 in the processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0074] The UE 100 configured in this manner performs wireless communication with a base station 200 that manages a cell in a mobile communication system. The receiver 110 receives SSBs that are transmitted from the base station 200 using beamforming and to which beam sweeping, which switches the transmission beam direction at predetermined time intervals, is applied. In this embodiment, the receiver 110 receives at least one of N SSBs that are simultaneously transmitted at different frequencies within the cell band. The controller 130 performs a cell search based on the SSBs received by the receiver 110.

[0075] In this embodiment, the receiver 110 receives at least one of N SSBs simultaneously transmitted at different frequencies and in different transmission beam directions (different BF patterns) within the cell band. Also, the receiver 110 receives a first group of SSBs at a first frequency within the cell band and a second group of SSBs at a second frequency within the cell band during a periodically occurring SS burst period.

[0076] Furthermore, in this embodiment, the receiving unit 110 receives from the base station 200 N pieces of configuration information indicating parameters of N SSBs simultaneously transmitted at different frequencies. Here, each of the N pieces of configuration information may be OffsetToPointA, i.e., information indicating, on a resource block basis, the frequency offset between the lowest-frequency subcarrier of the corresponding SSB and a reference point of the resource block grid. Each of the N pieces of configuration information may be Kssb(ssb-SubcarrierOffset), i.e., information indicating, on a subcarrier basis, the frequency offset between the lowest-frequency subcarrier of the corresponding SSB and the lower-frequency boundary of the resource block to which the subcarrier belongs. Each of the N pieces of configuration information may be absoluteFrequencySSB, i.e., information indicating the frequency of the corresponding SSB.

[0077] (5) System Operation Example FIG. 14 is a diagram showing an operation example of the base station 200 (network node) according to this embodiment.

[0078] In step S11, the base station 200 uses beamforming to transmit SSBs used in a cell search performed by the UE 100. The base station 200 simultaneously transmits N SSBs at different frequencies and with different BF patterns within the band of its own cell.

[0079] In step S12, the base station 200 checks whether the SS burst period (i.e., beam sweeping) has ended. Specifically, the base station 200 checks whether the transmission of all SSBs to be transmitted in the current SS burst period has ended.

[0080] If the SS burst period has not ended (step S12: NO), in step S13, the base station 200 switches the transmission beam direction (BF pattern) of the N SSBs, and returns the process to step S11.

[0081] If the SS burst period has ended (step S12: YES), base station 200 checks in step S14 whether the next SS burst period has started. If the next SS burst period has started (step S14: YES), base station 200 returns to step S11 and simultaneously transmits N SSBs at different frequencies and with different BF patterns within the band of its own cell.

[0082] FIG. 15 is a diagram illustrating an example of the operation of the UE 100 (user equipment) according to this embodiment.

[0083] In step S21, the UE 100 receives an SSB transmitted from the base station 200 by beamforming and to which beam sweeping, which switches the transmission beam direction at predetermined time intervals, is applied. The UE 100 receives at least one of N SSBs simultaneously transmitted at different frequencies within the cell band.

[0084] In step S22, the UE 100 performs a cell search based on the received SSB. Specifically, the UE 100 obtains time and frequency synchronization with a cell and detects a cell ID of the cell.

[0085] In step S23, the UE 100 measures the reception quality (for example, RSRP) of the received SSB.

[0086] In step S24, the UE 100 determines whether an SSB whose reception quality satisfies a predetermined condition has been identified. If an SSB whose reception quality satisfies the predetermined condition has not been identified (step S24: NO), the UE 100 returns the process to step S21.

[0087] On the other hand, if an SSB whose reception quality satisfies the predetermined condition is identified (step S24: YES), in step S25, an RA preamble is transmitted in the RA occasion associated with the identified SSB.

[0088] (6) 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.

[0089] In the above embodiment, 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.

[0090] The term "network 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). A network node may also be configured by a combination of at least a part of a core network device and at least a part of a base station.

[0091] A program may be provided that causes a computer to execute each process performed by the UE 100 or the base station 200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100 or the base station 200 may be integrated, and at least a part of the UE 100 or the base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC).

[0092] The functions performed by the UE 100 or the base station 200 (network node) may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the described functions. A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may also be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, or means refers to hardware that is programmed to perform the described functions or that executes the described functions. The hardware may be any hardware disclosed herein or any hardware known to be programmed or capable of performing the described functions. If the hardware is a processor, the circuitry, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0093] 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.

[0094] 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.

[0095] (7) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0096] (Supplementary Note 1) A network node that manages cells in a mobile communication system, comprising: a transmitter that transmits synchronization signal blocks used in cell search performed by a user device by beamforming; and a controller that performs beam sweeping to switch the transmission beam direction of the synchronization signal blocks at predetermined time intervals, wherein the controller controls the transmitter to simultaneously transmit N (N: an integer of 2 or more) synchronization signal blocks at different frequencies within the band of the cell.

[0097] (Supplementary Note 2) The network node according to Supplementary Note 1, wherein the control unit controls the transmission unit to simultaneously transmit the N synchronization signal blocks at different frequencies and in different transmission beam directions within a band of the cell.

[0098] (Supplementary Note 3) The network node according to Supplementary Note 1 or 2, wherein the transmitter transmits a first synchronization signal block group at a first frequency within the band of the cell and a second synchronization signal block group at a second frequency within the band of the cell during a synchronization signal burst period that occurs periodically.

[0099] (Supplementary Note 4) The network node according to Supplementary Note 3, wherein the control unit controls the beam sweeping so that, within the synchronization signal burst period, the first synchronization signal block group covers a first portion of a coverage area of ​​the cell and the second synchronization signal block group covers a second portion of the coverage area.

[0100] (Supplementary Note 5) The network node according to Supplementary Note 3, wherein the control unit assigns identifiers to the synchronization signal blocks so that identifiers of the synchronization signal blocks in the first synchronization signal block group do not overlap with identifiers of the synchronization signal blocks in the second synchronization signal block group.

[0101] (Supplementary Note 6) The control unit assigns identifiers to the synchronization signal blocks so that identifiers of the synchronization signal blocks of the first synchronization signal block group and identifiers of the synchronization signal blocks of the second synchronization signal block group at least partially overlap, and assigns different frequency indexes to the synchronization signal blocks of the first synchronization signal block group and the synchronization signal blocks of the second synchronization signal block group. The network node described in Supplementary Note 3.

[0102] (Supplementary Note 7) The network node according to any one of Supplementary Notes 1 to 6, wherein the transmitter transmits N pieces of configuration information indicating parameters of N pieces of the synchronization signal blocks to be simultaneously transmitted at different frequencies.

[0103] (Supplementary Note 8) The network node according to Supplementary Note 7, wherein each of the N pieces of configuration information is information indicating, in resource block units, a frequency offset between a subcarrier on the lowest frequency side of a corresponding synchronization signal block and a reference point of a resource block grid.

[0104] (Supplementary Note 9) The network node according to Supplementary Note 7, wherein each of the N pieces of configuration information is information indicating, on a subcarrier-by-subcarrier basis, a frequency offset between the lowest frequency subcarrier of a corresponding synchronization signal block and the lower frequency boundary of a resource block to which the subcarrier belongs.

[0105] (Supplementary Note 10) The network node according to Supplementary Note 7, wherein each of the N pieces of configuration information is information indicating a frequency of a corresponding synchronization signal block.

[0106] (Supplementary Note 11) A user equipment that performs wireless communication with a network node that manages a cell in a mobile communication system, comprising: a receiver that receives a synchronization signal block that is transmitted from the network node by beamforming and to which beam sweeping that switches the transmission beam direction at predetermined time intervals is applied; and a controller that performs cell search based on the synchronization signal block, wherein the receiver receives at least one of N (N: an integer of 2 or more) synchronization signal blocks that are simultaneously transmitted at different frequencies within the band of the cell.

[0107] (Supplementary Note 12) The user equipment according to Supplementary Note 11, wherein the receiving unit receives at least one of the N synchronization signal blocks simultaneously transmitted at different frequencies and in different transmission beam directions within a band of the cell.

[0108] (Supplementary Note 13) The user equipment according to Supplementary Note 12, wherein the receiving unit receives a first synchronization signal block group at a first frequency within the band of the cell and a second synchronization signal block group at a second frequency within the band of the cell during a synchronization signal burst period that occurs periodically.

[0109] (Supplementary Note 14) The user device according to Supplementary Note 13, wherein identifiers are assigned to the synchronization signal blocks so that the identifiers of the synchronization signal blocks in the first synchronization signal block group do not overlap with the identifiers of the synchronization signal blocks in the second synchronization signal block group.

[0110] (Supplementary Note 15) The user device described in Supplementary Note 13, wherein identifiers are assigned to the synchronization signal blocks so that identifiers of the synchronization signal blocks of the first synchronization signal block group and identifiers of the synchronization signal blocks of the second synchronization signal block group at least partially overlap, and different frequency identifiers are assigned to the synchronization signal blocks of the first synchronization signal block group and the synchronization signal blocks of the second synchronization signal block group.

[0111] (Supplementary Note 16) The user equipment according to any one of Supplementary Notes 11 to 15, wherein the receiving unit receives, from the network node, N pieces of configuration information indicating parameters of the N synchronization signal blocks simultaneously transmitted on different frequencies.

[0112] (Supplementary Note 17) The user equipment according to Supplementary Note 16, wherein each of the N pieces of configuration information is information indicating, in units of resource blocks, a frequency offset between a subcarrier on the lowest frequency side of a corresponding synchronization signal block and a reference point of a resource block grid.

[0113] (Supplementary Note 18) The user equipment according to Supplementary Note 16, wherein each of the N pieces of configuration information is information indicating, on a subcarrier-by-subcarrier basis, a frequency offset between a subcarrier on the lowest frequency side of a corresponding synchronization signal block and a boundary on the lower frequency side of a resource block to which the subcarrier belongs.

[0114] (Supplementary Note 19) The user equipment according to Supplementary Note 16, wherein each of the N pieces of setting information is information indicating a frequency of a corresponding synchronization signal block.

[0115] (Supplementary Note 20) A communication method used in a network node that manages cells in a mobile communication system, comprising: a step of transmitting a synchronization signal block used for cell search performed by a user device by beamforming; and a step of performing beam sweeping that switches the transmission beam direction of the synchronization signal block at predetermined time intervals, wherein the step of transmitting the synchronization signal block includes a step of simultaneously transmitting N (N: integer equal to or greater than 2) synchronization signal blocks at different frequencies within the band of the cell.

[0116] (Supplementary Note 21) A communication method used by a user equipment that performs wireless communication with a network node that manages a cell in a mobile communication system, the communication method comprising: a step of receiving a synchronization signal block that is transmitted from the network node by beamforming and to which beam sweeping that switches the transmission beam direction at predetermined time intervals is applied; and a step of performing a cell search based on the synchronization signal block, wherein the step of receiving the synchronization signal block includes a step of receiving at least one of N (N: an integer equal to or greater than 2) synchronization signal blocks that are simultaneously transmitted at different frequencies within the band of the cell.

[0117] 1: Network 10: RAN 20: CN 100: UE 110: Receiving unit 120: Transmitting unit 130: Control unit 140: Wireless communication unit 200: Base station 210: Transmitting unit 220: Receiving unit 230: Control unit 240: NW communication unit 250: Wireless communication unit 300: CN device

Claims

1. A network node that manages cells in a mobile communication system, A transmitting unit that transmits a synchronization signal block used for cell search performed by the user device by beamforming, The system includes a control unit that performs beam sweeping, which switches the transmission beam direction of the synchronization signal block at predetermined time intervals, The control unit controls the transmission unit to simultaneously transmit N (N: an integer of 2 or more) of the synchronization signal blocks at different frequencies within the bandwidth of the cell. The transmitting unit transmits a first set of synchronization signal blocks at a first frequency within the cell's bandwidth and a second set of synchronization signal blocks at a second frequency within the cell's bandwidth during a periodically occurring synchronization signal burst period. The control unit assigns identifiers to the synchronization signal blocks such that the identifiers of the synchronization signal blocks in the first synchronization signal block group and the identifiers of the synchronization signal blocks in the second synchronization signal block group do not overlap. Network node.

2. The control unit controls the transmitting unit to simultaneously transmit N of the synchronization signal blocks within the cell's bandwidth at different frequencies and in different transmission beam directions. The network node according to claim 1.

3. The control unit controls the beam sweeping during the synchronization signal burst period such that the first synchronization signal block group covers a first portion of the coverage area of ​​the cell and the second synchronization signal block group covers a second portion of the coverage area. The network node according to claim 1.

4. A network node for managing cells in a mobile communication system, A transmitting unit that transmits a synchronization signal block used for cell search performed by the user device by beamforming, The system includes a control unit that performs beam sweeping, which switches the transmission beam direction of the synchronization signal block at predetermined time intervals, The control unit controls the transmission unit to simultaneously transmit N (N: an integer of 2 or more) of the synchronization signal blocks at different frequencies within the bandwidth of the cell. The transmitting unit transmits N pieces of setting information indicating the parameters of N synchronization signal blocks that are transmitted simultaneously at different frequencies. Each of the N setting pieces of information indicates, on a resource block basis, the frequency offset between the lowest-frequency subcarrier of the corresponding synchronization signal block and the reference point of the resource block grid. Network node.

5. A network node for managing cells in a mobile communication system, A transmitting unit that transmits a synchronization signal block used for cell search performed by the user device by beamforming, The system includes a control unit that performs beam sweeping, which switches the transmission beam direction of the synchronization signal block at predetermined time intervals, The control unit controls the transmission unit to simultaneously transmit N (N: an integer of 2 or more) of the synchronization signal blocks at different frequencies within the bandwidth of the cell. The transmitting unit transmits N pieces of setting information indicating the parameters of N synchronization signal blocks that are transmitted simultaneously at different frequencies. Each of the N setting pieces of information indicates, on a subcarrier basis, the frequency offset between the lowest-frequency subcarrier of the corresponding synchronization signal block and the low-frequency boundary of the resource block to which that subcarrier belongs. Network node.

6. A network node for managing cells in a mobile communication system, A transmitting unit that transmits a synchronization signal block used for cell search performed by the user device by beamforming, The system includes a control unit that performs beam sweeping, which switches the transmission beam direction of the synchronization signal block at predetermined time intervals, The control unit controls the transmission unit to simultaneously transmit N (N: an integer of 2 or more) of the synchronization signal blocks at different frequencies within the bandwidth of the cell. The transmitting unit transmits a first set of synchronization signal blocks at a first frequency within the cell's bandwidth and a second set of synchronization signal blocks at a second frequency within the cell's bandwidth during a periodically occurring synchronization signal burst period. The control unit assigns identifiers to the synchronization signal blocks such that the identifiers of the synchronization signal blocks in the first synchronization signal block group and the identifiers of the synchronization signal blocks in the second synchronization signal block group overlap at least partially, and assigns different frequency indices to the synchronization signal blocks in the first synchronization signal block group and the synchronization signal blocks in the second synchronization signal block group. Network node.

7. A user device that performs wireless communication with a network node that manages a cell in a mobile communication system, A receiving unit that receives a synchronization signal block transmitted from the network node by beamforming and to which beam sweeping is applied, which switches the direction of the transmitted beam at predetermined time intervals, The system includes a control unit that performs a cell search based on the aforementioned synchronization signal block, The receiving unit receives at least one of the N (N: an integer of 2 or more) synchronization signal blocks that are transmitted simultaneously at different frequencies within the bandwidth of the cell. The receiving unit receives a first set of synchronization signal blocks at a first frequency within the cell's bandwidth during a periodically occurring synchronization signal burst period, and receives a second set of synchronization signal blocks at a second frequency within the cell's bandwidth. Identifiers are assigned to the synchronization signal blocks such that the identifiers of the synchronization signal blocks in the first synchronization signal block group and the identifiers of the synchronization signal blocks in the second synchronization signal block group do not overlap. User device.

8. The receiving unit receives at least one of the N synchronization signal blocks that are transmitted simultaneously within the cell's bandwidth at different frequencies and in different transmission beam directions. The user device according to claim 7.

9. A user device that performs wireless communication with a network node that manages a cell in a mobile communication system, A receiving unit that receives a synchronization signal block transmitted from the network node by beamforming and to which beam sweeping is applied, which switches the direction of the transmitted beam at predetermined time intervals, The system includes a control unit that performs a cell search based on the aforementioned synchronization signal block, The receiving unit receives at least one of the N (N: an integer of 2 or more) synchronization signal blocks that are transmitted simultaneously at different frequencies within the bandwidth of the cell. The receiving unit receives N pieces of configuration information from the network node that indicate the parameters of N synchronization signal blocks transmitted simultaneously at different frequencies. Each of the N setting pieces of information indicates, on a resource block basis, the frequency offset between the lowest-frequency subcarrier of the corresponding synchronization signal block and the reference point of the resource block grid. User device.

10. A user device that performs wireless communication with a network node that manages a cell in a mobile communication system, A receiving unit that receives a synchronization signal block transmitted from the network node by beamforming and to which beam sweeping is applied, which switches the direction of the transmitted beam at predetermined time intervals, The system includes a control unit that performs a cell search based on the aforementioned synchronization signal block, The receiving unit receives at least one of the N (N: an integer of 2 or more) synchronization signal blocks that are transmitted simultaneously at different frequencies within the bandwidth of the cell. The receiving unit receives N pieces of configuration information from the network node that indicate the parameters of N synchronization signal blocks transmitted simultaneously at different frequencies. Each of the N setting pieces of information indicates, on a subcarrier basis, the frequency offset between the lowest-frequency subcarrier of the corresponding synchronization signal block and the low-frequency boundary of the resource block to which that subcarrier belongs. User device.

11. A user device that performs wireless communication with a network node that manages a cell in a mobile communication system, A receiving unit that receives a synchronization signal block transmitted from the network node by beamforming and to which beam sweeping is applied, which switches the direction of the transmitted beam at predetermined time intervals, The system includes a control unit that performs a cell search based on the aforementioned synchronization signal block, The receiving unit receives at least one of the N (N: an integer of 2 or more) synchronization signal blocks that are transmitted simultaneously at different frequencies within the bandwidth of the cell. The receiving unit receives a first set of synchronization signal blocks at a first frequency within the cell's bandwidth during a periodically occurring synchronization signal burst period, and receives a second set of synchronization signal blocks at a second frequency within the cell's bandwidth. Identifiers are assigned to the synchronization signal blocks such that the identifiers of the synchronization signal blocks in the first synchronization signal block group and the identifiers of the synchronization signal blocks in the second synchronization signal block group overlap at least partially. The synchronization signal blocks of the first synchronization signal block group and the synchronization signal blocks of the second synchronization signal block group are assigned different frequency identifiers. User device.

12. A communication method used in a network node that manages cells in a mobile communication system, A transmission step in which a synchronization signal block used for cell search performed by the user device is transmitted by beamforming, The control step includes performing beam sweeping, which switches the transmission beam direction of the synchronization signal block at predetermined time intervals. The transmission step includes the step of simultaneously transmitting N (N: an integer of 2 or more) of the synchronization signal blocks at different frequencies within the bandwidth of the cell. In the transmission step, during the periodically occurring synchronization signal burst period, a first synchronization signal block group is transmitted at a first frequency within the cell's bandwidth, and a second synchronization signal block group is transmitted at a second frequency within the cell's bandwidth. In the control step, identifiers are assigned to the synchronization signal blocks such that the identifiers of the synchronization signal blocks in the first synchronization signal block group and the identifiers of the synchronization signal blocks in the second synchronization signal block group do not overlap. Communication method.

13. A communication method used in a network node that manages a cell in a mobile communication system, A transmission step in which a synchronization signal block used for cell search performed by the user device is transmitted by beamforming, The control step includes performing beam sweeping, which switches the transmission beam direction of the synchronization signal block at predetermined time intervals. The transmission step includes the step of simultaneously transmitting N (N: an integer of 2 or more) of the synchronization signal blocks at different frequencies within the bandwidth of the cell. In the transmission step, N pieces of setting information indicating the parameters of N synchronization signal blocks to be transmitted simultaneously at different frequencies are transmitted. Each of the N setting pieces of information indicates, on a resource block basis, the frequency offset between the lowest-frequency subcarrier of the corresponding synchronization signal block and the reference point of the resource block grid. Communication method.

14. A communication method used in a network node that manages cells in a mobile communication system, A transmission step in which a synchronization signal block used for cell search performed by the user device is transmitted by beamforming, The control step includes performing beam sweeping, which switches the transmission beam direction of the synchronization signal block at predetermined time intervals. The transmission step includes the step of simultaneously transmitting N (N: an integer of 2 or more) of the synchronization signal blocks at different frequencies within the bandwidth of the cell. In the transmission step, N pieces of setting information indicating the parameters of N synchronization signal blocks to be transmitted simultaneously at different frequencies are transmitted. Each of the N setting pieces of information indicates, on a subcarrier basis, the frequency offset between the lowest-frequency subcarrier of the corresponding synchronization signal block and the low-frequency boundary of the resource block to which that subcarrier belongs. Communication method.

15. A communication method used in a network node that manages a cell in a mobile communication system, A transmission step in which a synchronization signal block used for cell search performed by the user device is transmitted by beamforming, The control step includes performing beam sweeping, which switches the transmission beam direction of the synchronization signal block at predetermined time intervals. The transmission step includes the step of simultaneously transmitting N (N: an integer of 2 or more) of the synchronization signal blocks at different frequencies within the bandwidth of the cell. In the transmission step, during the periodically occurring synchronization signal burst period, a first synchronization signal block group is transmitted at a first frequency within the cell's bandwidth, and a second synchronization signal block group is transmitted at a second frequency within the cell's bandwidth. In the control step, identifiers are assigned to the synchronization signal blocks such that the identifiers of the synchronization signal blocks in the first synchronization signal block group and the identifiers of the synchronization signal blocks in the second synchronization signal block group overlap at least partially, and different frequency indices are assigned to the synchronization signal blocks in the first synchronization signal block group and the synchronization signal blocks in the second synchronization signal block group. Communication method.

16. A communication method used in a user device that performs wireless communication with a network node that manages a cell in a mobile communication system, A receiving step of receiving a synchronization signal block transmitted from the network node by beamforming and to which beam sweeping is applied, which switches the transmission beam direction at predetermined time intervals, The step includes performing a cell search based on the aforementioned synchronization signal block, The receiving step includes receiving at least one of the N (N: an integer of 2 or more) synchronization signal blocks that are transmitted simultaneously at different frequencies within the bandwidth of the cell. In the receiving step, during the periodically occurring synchronization signal burst period, a first synchronization signal block group is received at a first frequency within the cell's bandwidth, and a second synchronization signal block group is received at a second frequency within the cell's bandwidth. Identifiers are assigned to the synchronization signal blocks such that the identifiers of the synchronization signal blocks in the first synchronization signal block group and the identifiers of the synchronization signal blocks in the second synchronization signal block group do not overlap. Communication method.

17. A communication method for use in a user device that performs wireless communication with a network node that manages a cell in a mobile communication system, A receiving step of receiving a synchronization signal block transmitted from the network node by beamforming and to which beam sweeping is applied, which switches the transmission beam direction at predetermined time intervals, The step includes performing a cell search based on the aforementioned synchronization signal block, The receiving step includes receiving at least one of the N (N: an integer of 2 or more) synchronization signal blocks that are transmitted simultaneously at different frequencies within the bandwidth of the cell. In the receiving step, N pieces of configuration information indicating the parameters of N synchronization signal blocks transmitted simultaneously at different frequencies are received from the network node. Each of the N setting pieces of information indicates, on a resource block basis, the frequency offset between the lowest-frequency subcarrier of the corresponding synchronization signal block and the reference point of the resource block grid. Communication method.

18. A communication method for use in a user device that performs wireless communication with a network node that manages a cell in a mobile communication system, A receiving step of receiving a synchronization signal block transmitted from the network node by beamforming and to which beam sweeping is applied, which switches the transmission beam direction at predetermined time intervals, The step includes performing a cell search based on the aforementioned synchronization signal block, The receiving step includes receiving at least one of the N (N: an integer of 2 or more) synchronization signal blocks that are transmitted simultaneously at different frequencies within the bandwidth of the cell. In the receiving step, N pieces of configuration information indicating the parameters of N synchronization signal blocks transmitted simultaneously at different frequencies are received from the network node. Each of the N setting pieces of information indicates, on a subcarrier basis, the frequency offset between the lowest-frequency subcarrier of the corresponding synchronization signal block and the low-frequency boundary of the resource block to which that subcarrier belongs. Communication method.

19. A communication method for use in a user device that performs wireless communication with a network node that manages a cell in a mobile communication system, A receiving step of receiving a synchronization signal block transmitted from the network node by beamforming and to which beam sweeping is applied, which switches the transmission beam direction at predetermined time intervals, The step includes performing a cell search based on the aforementioned synchronization signal block, The receiving step includes receiving at least one of the N (N: an integer of 2 or more) synchronization signal blocks that are transmitted simultaneously at different frequencies within the bandwidth of the cell. In the receiving step, during the periodically occurring synchronization signal burst period, a first synchronization signal block group is received at a first frequency within the cell's bandwidth, and a second synchronization signal block group is received at a second frequency within the cell's bandwidth. Identifiers are assigned to the synchronization signal blocks such that the identifiers of the synchronization signal blocks in the first synchronization signal block group and the identifiers of the synchronization signal blocks in the second synchronization signal block group overlap at least partially. The synchronization signal blocks of the first synchronization signal block group and the synchronization signal blocks of the second synchronization signal block group are assigned different frequency identifiers. Communication method.