Communication device, base station, and communication method

Abstract

To provide a user device and a communication control method that appropriately adjust uplink transmission timing in an active BWP (bandwidth part) even if a BWP in which no SSB (synchronization signal and physical broadcast channel block) is transmitted is set.SOLUTION: A user device 100 communicates with a base station 200 in a BWP which is a part of the entire bandwidth of a cell of the base station. The user device communicates using an active BWP used for communication with the base station among a plurality of BWPs set for the user device and, when the active BWP is a BWP with SSB which is a BWP in which SSB is being transmitted from the base station, retains downlink frame timing in the BWP with SSB. When the active BWP is a BWP without SSB which is a BWP in which no SSB is being transmitted from the base station, the user device adjusts uplink transmission timing in the active BWP based on the retained downlink frame timing.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a user device and a communication control method used in a mobile communication system.

Background Art

[0002] In a fifth-generation (5G) mobile communication system (5G system), communication between a user device and a base station using a bandwidth part (hereinafter, BWP), which is a part of the entire bandwidth of a cell, is defined. The user device communicates using the BWP (hereinafter, active BWP) used for communication with the base station. A plurality of BWPs can be set for each of the BWP for downlink communication (hereinafter, downlink BWP) and the BWP for uplink communication (hereinafter, uplink BWP) in the user device. When a plurality of BWPs are set in the user device, the active BWP is switched and used.

[0003] The base station transmits a synchronization signal and a physical broadcast channel block (hereinafter, SSB). The user device can grasp the downlink frame timing based on the SSB received from the base station. When performing uplink transmission in an uplink frame, the user device adjusts the timing of the uplink transmission based on the downlink frame timing corresponding to the uplink frame. By each of a plurality of user devices managed by the base station adjusting the timing of the uplink transmission, the base station can receive an uplink transmission signal from the plurality of user devices within a predetermined time range.

[0004] In recent years, in 3GPP, which is a standardization project for mobile communication systems, providing user equipment with limited communication capabilities (so-called Reduced capability NR device) in a 5G system has been under consideration. Since such user equipment does not have a plurality of receivers, during communication in a BWP, it is not possible to measure SSBs transmitted at frequencies other than the BWP. Therefore, it is conceivable to set a BWP for the user equipment where the SSB is transmitted. However, since the BWP where the SSB is transmitted is limited, traffic congestion may occur when a large number of user equipment concentrate on such a limited active BWP.

[0005] Therefore, in order to avoid traffic congestion, it is desirable that a BWP where the SSB is not transmitted can be set for the user equipment in the entire bandwidth of the cell (see, for example, Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

[0007] However, when the user equipment switches the BWP where the SSB is not transmitted among the set multiple BWPs to the active BWP, since the SSB is not transmitted in the active BWP after the switch, it is not possible to grasp the downlink frame timing of the active BWP after the switch. Therefore, when the user equipment performs uplink transmission in the active BWP, there is a problem that the timing of the uplink transmission cannot be appropriately adjusted.

[0008] Therefore, an object of the present invention is to provide a user equipment and a communication control method capable of appropriately adjusting the timing of uplink transmission in an active BWP even when a BWP where the SSB is not transmitted is set.

Means for Solving the Problem

[0009] A user equipment according to an aspect of the present disclosure communicates with a base station in a BWP which is a part of the entire bandwidth of a cell of the base station. The user equipment includes a communication unit that performs the communication using an active BWP used for the communication with the base station among a plurality of BWPs set in the user equipment, and a control unit that holds downlink frame timing in the BWP with SSB when the active BWP is a BWP with SSB which is the BWP in which the SSB is transmitted from the base station. When the active BWP is a BWP without SSB which is the BWP in which the SSB is not transmitted from the base station, the control unit adjusts the timing of uplink transmission in the active BWP based on the held downlink frame timing.

[0010] A communication control method according to an aspect of the present disclosure is executed by a user equipment that communicates with a base station in a BWP which is a part of the entire bandwidth of a cell of the base station. The communication control method includes a step of performing the communication using an active BWP used for the communication with the base station among a plurality of BWPs set in the user equipment, a step of holding downlink frame timing in the BWP with SSB when the active BWP is a BWP with SSB which is the BWP in which the SSB is transmitted from the base station, and a step of adjusting the timing of uplink transmission in the active BWP based on the held downlink frame timing when the active BWP is a BWP without SSB which is the BWP in which the SSB is not transmitted from the base station.

Advantages of the Invention

[0011] According to an aspect of the present invention, it is possible to provide a user equipment and a communication control method capable of appropriately adjusting the timing of uplink transmission in an active BWP even when a BWP in which an SSB is not transmitted is set.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the present specification and drawings, elements that can be similarly described may be denoted by the same or similar reference numerals, and redundant description may be omitted.

[0014] (1) Configuration of the System (1.1) System Overview Referring to FIG. 1, an example of the configuration of the system 1 according to an embodiment of the present disclosure will be described. The system 1 is, for example, a mobile communication system compliant with the technical specification (Technical Specification: TS) of 3GPP, which is a standardization project of a mobile communication system. Hereinafter, as the system 1, a fifth-generation system (5th Generation System: 5GS) of the 3GPP standard, that is, a mobile communication system based on NR (New Radio) will be described as an example. Note that the system 1 is not limited to this example. The system 1 may be a system compliant with the TS of either LTE (Long Term Evolution) or other generation systems (for example, the sixth generation) of the 3GPP standard. The system 1 may be a system compliant with the TS of a standard other than the 3GPP standard.

[0015] As shown in FIG. 1, the system 1 includes a 5G radio access network (so-called Next Generation Radio Access Network: NG-RAN) 20, a 5G core network (5G Core Network: 5GC) 30, and a user equipment (User Equipment: UE) 100.

[0016] The NG-RAN 20 includes a base station (Base Station: BS) 200, which is a node of the radio access network. The BS 200 can communicate with the UE 100 located within the coverage area of the BS 200. The BS 200 communicates with the UE 100, for example, using the RAN protocol stack. The protocol stack includes, for example, an RRC (Radio Resource Control) layer, an SDAP (Service Data Adaptation Protocol) layer, a PDCP (Packet Data Convergence Protocol) layer, an RLC (Radio Link Control) layer, a MAC (Medium Access Control) layer, and a physical (Physical: PHY) layer. However, in the case of LTE, the SDAP layer may not be present.

[0017] BS200 provides, for example, NR user plane and control plane protocol terminations towards UE100 and is a gNB connected to 5GC30 via the NG interface. Note that BS200 may be an eNB that provides, for example, E-UTRA user plane and control plane protocol terminations towards UE100 in LTE.

[0018] BS200 may include a plurality of units. The plurality of units may include a first unit that hosts higher layers included in the protocol stack and a second unit that hosts lower layers included in the protocol stack. The higher layers may include the RRC layer, the SDAP layer, and the PDCP layer, and the lower layers may include the RLC layer, the MAC layer, and the PHY layer. The first unit may be a CU (central unit), and the second unit may be a DU (Distributed Unit). The plurality of units may include a third unit that performs processing below the PHY layer. The second unit may perform processing above the PHY layer. The third unit may be an RU (Radio Unit). BS200 may be one of the plurality of units and may be connected to other units among the plurality of units. Also, BS200 may be an IAB (Integrated Access and Backhaul) donor or an IAB node.

[0019] 5GC30 includes a core network device 300. The core network device 300 includes, for example, an AMF (Access and Mobility Management Function) and / or a UPF (User Plane Function). The AMF performs mobility management of UE100. The UPF provides functions specialized for U-plane processing. The AMF and the UPF are connected to BS200 via the NG interface.

[0020] UE100 can communicate with BS200 when it is located within the coverage area of BS200. UE100 can communicate with BS200 using the protocol stack described above.

[0021] UE100 may be any device used by a user. UE100 is, for example, a mobile wireless communication device such as a mobile phone terminal like a smartphone, a tablet terminal, a notebook PC, a communication module, or a communication card. Also, UE100 may be a vehicle (e.g., a car, a train, etc.) or a device provided in a vehicle. UE100 may be a transportation aircraft other than a vehicle (e.g., a ship, an airplane, etc.) or a device provided in a transportation aircraft other than a vehicle. Also, UE100 may be a sensor or a device provided in a sensor. Note that UE100 may be called by another name such as a mobile station, a mobile terminal, a mobile device, a mobile unit, a subscriber station, a subscriber terminal, a subscriber device, a subscriber unit, a wireless station, a wireless terminal, a wireless device, a wireless unit, a remote station, a remote terminal, a remote device, or a remote unit.

[0022] UE100 may be a user equipment with limited communication capabilities (so-called Reduced capability NR device: RedCap UE). The RedCap UE may be a UE with reduced device cost and complexity compared to, for example, a UE that meets the high-performance high-speed large-capacity (enhanced Mobile Broadband: eMBB) and ultra-reliable low-latency (Ultra-Reliable and Low Latency Communications: URLLC) of Rel-15 or Rel-16. The RedCap UE may be able to communicate at a communication speed higher than the communication speed defined by the LPWA (Low Power Wide Area) standard (for example, LTE Cat.1 / 1bis, LTE Cat.M1 (LTE-M), LTE Cat.NB1 (NB-IoT)). The RedCap UE may be able to communicate with a bandwidth greater than the bandwidth defined by the LPWA standard. The RedCap UE may have a limited bandwidth used for communication compared to a Rel-15 or Rel-16 UE. In FR1 (Frequency Range 1), for example, the maximum bandwidth of the RedCap UE may be 20 MHz and may be 40 MHz under certain conditions. In FR2 (Frequency Range 2), for example, the maximum bandwidth of the RedCap UE may be 100 MHz. The RedCap UE may have only one receiver (so-called Rx chain) for receiving radio signals. The RedCap UE may be, for example, an industrial wireless sensor, a video surveillance device, or a wearable device.

[0023] (1.2) Configuration of User Equipment Referring to FIG. 2, an example of the configuration of UE100 according to an embodiment of the present disclosure will be described. UE100 includes a communication unit 110 and a control unit 120.

[0024] The communication unit 110 communicates with other communication devices by transmitting and receiving signals. For example, the communication unit 110 receives a wireless signal from the BS200 and transmits a wireless signal to the BS200. Also, the communication unit 110 may, for example, receive a wireless signal from another UE and transmit a wireless signal to another UE.

[0025] The communication unit 110 may include one or more receivers for receiving wireless signals and one or more transmitters for transmitting wireless signals. In the following, a configuration in which the communication unit 110 includes only one receiver is mainly assumed. The receiver and the transmitter may include an antenna and an RF circuit. The antenna converts a signal into a radio wave and radiates the radio wave into space. Also, the antenna receives a radio wave in space and converts the radio wave into a signal. The antenna may include a transmitting antenna and a receiving antenna. The antenna may include an antenna for both transmission and reception. The antenna may include a plurality of antenna elements. The RF circuit performs analog processing of signals transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, and the like.

[0026] The control unit 120 performs various controls in the UE100. For example, the control unit 120 controls communication with the BS200 or another UE100 via the communication unit 110. The operations of the UE100 described later may be operations under the control of the control unit 120.

[0027] The control unit 120 may include one or more processors capable of executing a program and a memory for storing the program. The one or more processors may execute the program to perform the operations of the control unit 120. The program may be a program for causing the processor to execute the operations of the control unit 120.

[0028] The processor performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes the processing of the RAN protocol stack. The processor may be a single processor. The processor may include a plurality of processors. The plurality of processors may include a baseband processor that performs digital processing and one or more processors that perform other processing. The memory stores programs executed by the processor, parameters related to the programs, and data related to the programs. The memory may include at least one of ROM (Read Only Memory), EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), RAM (Random Access Memory), and flash memory. All or part of the memory may be included in the processor.

[0029] Note that in the following, the operations of the functional units included in the UE100 (specifically, the communication unit 110 and the control unit 120) may be described as the operations of the UE100.

[0030] (1.3) Configuration of the base station Referring to FIG. 3, an example of the configuration of the BS200 according to an embodiment of the present disclosure will be described. The BS200 includes a communication unit 210 and a control unit 220.

[0031] The communication unit 210 communicates with other communication devices by transmitting and receiving signals. The communication unit 210 includes a wireless communication unit 212 and a network communication unit 214.

[0032] The wireless communication unit 212 transmits and receives signals to and from a wireless communication device. The wireless communication unit 212, for example, receives a wireless signal from the UE 100 and transmits a wireless signal to the UE 100. The wireless communication unit 212 may include one or more receivers for receiving wireless signals and one or more transmitters for transmitting wireless signals. The receiver and the transmitter may include an antenna and an RF circuit. The antenna converts a signal into a radio wave and radiates the radio wave into space. Also, the antenna receives a radio wave in space and converts the radio wave into a signal. The antenna may include a transmitting antenna and a receiving antenna. The antenna may include an antenna for both transmission and reception. The antenna may be a directional antenna. The antenna may include a plurality of antenna elements. The RF circuit performs analog processing of signals transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, and the like.

[0033] The network communication unit 214 transmits and receives signals to and from a network. The network communication unit 214, for example, receives a signal from an adjacent base station connected via an Xn interface, which is a base station-to-base station interface, and transmits a signal to the adjacent base station. Also, the network communication unit 214, for example, receives a signal from a core network device 300 connected via an NG interface and transmits a signal to the core network device 300. The network communication unit 214 may include a network interface. The network interface may be, for example, a network adapter.

[0034] The control unit 220 performs various controls in the BS 200. The control unit 220, for example, controls communication with the UE 100 via the wireless communication unit 212. Also, the control unit 220, for example, controls communication with nodes (for example, network nodes in the core network, adjacent base stations, core network devices 300) via the network communication unit 214. The operations of the BS 200 described later may be operations under the control of the control unit 220.

[0035] The control unit 220 may include one or more processors capable of executing a program and a memory for storing the program. The one or more processors may execute the program to perform the operations of the control unit 220. The program may be a program for causing the processor to execute the operations of the control unit 220.

[0036] The processor performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of the RAN protocol stack. The processor may be a single processor. The processor may include a plurality of processors. The plurality of processors may include a baseband processor that performs digital processing and one or more processors that perform other processing. The memory stores a program executed by the processor, parameters related to the program, and data related to the program. The memory may include at least one of ROM, EPROM, EEPROM, RAM, and flash memory. All or part of the memory may be included in the processor.

[0037] Part or all of the control unit 220 may be virtualized. That is, part or all of the control unit 220 may be implemented as a virtual machine. In this case, part or all of the control unit 220 may operate as a virtual machine on a physical machine (i.e., hardware) including a processor and a memory, etc. and a hypervisor.

[0038] In the following, the operations of the functional units (communication unit 210 and control unit 220) provided in the BS200 may be described as the operations of the BS200.

[0039] (1.4) BWP (Bandwidth Part) UE100 and BS200 communicate using a BWP (Bandwidth Part) which is a part of the entire bandwidth of the cell. Specifically, BS200 sets one or more BWPs for UE100. BS200 can notify UE100 of the BWP (i.e., the active BWP) to be used for communication with BS200 among the set one or more BWPs. Specifically, BS200 can transmit to UE100 an identifier indicating the BWP to be activated at the time of setting, i.e., the BWP to be first used in communication with BS200. Also, for the control of switching from an active BWP to a non-active BWP (hereinafter, non-active BWP) and from a non-active BWP to an active BWP (so-called BWP switching), for example, a physical downlink control channel (e.g., downlink assignment, uplink assignment), a timer (i.e., bwp-InactivityTimer), RRC signaling, or a MAC entity, etc. is used.

[0040] The BWP includes an initial BWP and an individual BWP. The initial BWP is used at least for the initial access of UE100. The initial BWP is commonly used for a plurality of UE100s. The initial BWP includes an initial BWP for downlink communication (hereinafter, initial downlink BWP (Initial DL BWP)) and an initial BWP for uplink communication (hereinafter, initial uplink BWP (Initial UL BWP)). The value of the identifier (i.e., bwp-id) indicating each of the initial downlink BWP and the initial uplink BWP is 0.

[0041] UE100 can determine the initial BWP (i.e., the initial downlink BWP and the initial uplink BWP) in, for example, two ways. In the first method, UE100 determines the initial BWP based on CORESET#0 configured using the information included in the master information block (MIB) within the physical broadcast channel (PBCH). In the second method, UE100 determines the initial BWP based on the position and bandwidth in the frequency domain configured using the information included in the system information block (SIB). UE100 may apply the BWP determined by the first method for communication with BS200 until, for example, receiving message 4 in the random access procedure. After receiving message 4, UE100 may apply the BWP determined by the second method for communication with BS200.

[0042] The individual BWP is configured individually for UE100. The individual BWP includes an individual BWP for downlink communication (hereinafter, individual downlink BWP (UE dedicated DL BWP)) and an individual BWP for uplink communication (hereinafter, individual uplink BWP (UE dedicated UL BWP)). The value of the identifier indicating each of the individual downlink BWP and the individual uplink BWP is non-zero.

[0043] For UE100, an individual BWP is configured based on, for example, the information included in the RRC message (e.g., the information for the downlink BWP (i.e., BWP-Downlink) and the information for the uplink BWP (i.e., BWP-Uplink)). Each of the information for the downlink BWP and the information for the individual uplink BWP may include at least any one of the information indicating the position and bandwidth in the frequency domain (e.g., locationAndBadwidth), the information indicating the subcarrier spacing (e.g., subcarrierSpacing), and the information indicating whether to use an extended cyclic prefix (e.g., cyclicPrefix).

[0044] (1.5) Synchronization signal and physical broadcast channel block (SSB) In the time domain, SSB is composed of 4 OFDM symbols, and in the frequency domain, it is composed of 240 consecutive subcarriers. SSB is composed of a primary synchronization signal (hereinafter referred to as PSS) and a secondary synchronization signal (hereinafter referred to as SSS), and a physical broadcast channel (PBCH). Each of PSS and SSS occupies 1 OFDM symbol and 127 subcarriers. PBCH extends over 3 OFDM symbols and 240 subcarriers. The position of the resource element to which SSB is mapped is defined in the specification.

[0045] BS200 transmits SSB in the initial BWP (specifically, the initial downlink BWP). BS200 can transmit SSB periodically. UE100 can receive (i.e., detect) the SSB transmitted from BS200 in the initial downlink BWP and achieve time and / or frequency synchronization.

[0046] (1.6) Measurement UE100 is capable of making measurements based on the radio signals received from BS200. UE100 can perform measurements of radio quality (e.g., received power (so-called SS reference signal received power: SS-RSRP), received quality (so-called SS reference signal received quality: SS-RSRQ), signal-to-noise and interference ratio (so-called SS signal-to-noise and interference ratio: SS-SINR), etc.) based on, for example, SSB. Also, UE100 can perform measurements of radio quality (e.g., received power (so-called CSI reference signal received power : CSI-RSRP), received quality (so-called CSI reference signal received quality: CSI-RSRQ), etc.) based on, for example, a channel state information reference signal (hereinafter referred to as CSI-RS). CSI-RS is transmitted on a resource individually configured for UE100 (hereinafter referred to as CSI-RS resource). The CSI-RS resource can be configured in either the initial BWP or the individual BWP.

[0047] The UE 100 may use the measurement results for communication control with the BS 200. Also, the UE 100 may report the measurement results to the BS 200. When the UE 100 performs measurements based on the SSB, for example, it may report measurement results for each SSB, measurement results for each cell based on the SSB, and / or the SSB index, etc. Also, when the UE 100 performs measurements based on the CSI-RS, for example, it may report measurement results for each CSI-RS resource, measurement results for each cell based on the CSI-RS resource, and / or the CSI-RS resource identifier, etc. The UE 100 may report the measurement results periodically or triggered by a predetermined event. The UE 100 may report the measurement results on the physical uplink shared channel (PUSCH) in the uplink BWP, for example.

[0048] Note that for SSB based intra-frequency measurement at a frequency included in the cell's frequency range, when the BS 200 receives measurement gap request information from the UE 100, it may set the measurement gap according to the request information. When the BS 200 has not received the request information from the UE 100 and, outside the initial BWP, none of the multiple BWPs set for the UE 100 includes the frequency domain resources of the SSB associated with the initial BWP, the BS 200 may always provide the measurement gap setting for the UE 100.

[0049] (1.7) Adjustment of Uplink Transmission Timing The BS 200 controls the transmission timing of the uplink signal of each UE 100 to keep the reception timing of the uplink signal from each UE 100 within a predetermined time range within the cell it manages. The BS 200 determines the timing advance (hereinafter referred to as TA) for the UE 100 to adjust the transmission timing of the uplink signal. The BS 200 provides the determined TA to each UE 100.

[0050] UE100 adjusts the timing of the uplink transmission based on the downlink frame timing. UE100 uses TA to adjust the uplink frame timing with respect to the downlink frame. Specifically, as shown in FIG. 4, UE100 advances the i-th uplink frame by the time of (N TA +N TA,offset )T c with respect to the i-th downlink frame. N TA is the timing advance between the downlink and the uplink. N TA is a value for adjusting the timing notified from BS200 (serving cell). N TA,offset is a fixed offset value used to calculate the timing advance. N TA,offset is notified from BS200 (serving cell). If UE100 is not notified of N TA,offset from BS200, it may determine N TA,offset as a default value. T c is the basic time unit. T c is a predetermined fixed value. UE100 holds the information of T c in advance.

[0051] The downlink frame timing serving as the reference for adjusting the uplink transmission timing is the timing at the start of the downlink frame. Specifically, the downlink frame timing is defined as the time when the path first detected within the time of the downlink frame is received from BS200 (specifically, the reference cell). Note that the radio frames constituting the uplink frame and the downlink frame are composed of 10 subframes of 1 ms each. Each frame is divided into two half-frames of the same size consisting of 5 subframes.

[0052] UE100 can grasp the downlink frame timing in the BWP where the SSB is received by performing downlink timing synchronization using the synchronization signal included in the SSB transmitted in the BWP.

[0053] (2) System operation (2.1) Operation Example 1 Referring to FIG. 5, an operation example 1 of the UE 100 and the BS 200 according to an embodiment of the present disclosure will be described. The UE 100 is located within a serving cell managed by the BS 200. In this operation example 1, the case where the UE 100 is in the RRC idle state without an RRC connection between the RRC of the UE 100 and the RRC of the base station 200 will be described as an example.

[0054] In step S101, the BS 200 transmits an SSB in the serving cell. The BS 200 may transmit the SSB periodically in the initial BWP determined based on the SSB. The UE 100 receives the SSB from the BS 200.

[0055] In step S102, the UE 100 performs downlink timing synchronization using the synchronization signal included in the SSB transmitted from the BS 200. Specifically, the UE 100 detects the PSS included in the synchronization signal to identify the position of the SSS included in the synchronization signal. The UE 100 can determine the downlink frame timing by detecting the SSS. The UE 100 can hold the determined downlink frame timing. In this way, the UE 100 can grasp the downlink frame timing.

[0056] In step S103, the UE 100 transmits a message 1 (hereinafter, MSG1) to the BS 200. The UE 100 transmits, for example, MSG1 including a random access preamble on a physical random access channel (PRACH) in a random access procedure. The UE 100 may determine the initial BWP based on the MIB included in the SSB. The UE 100 may transmit MSG1 using the determined initial BWP. The BS 200 receives MSG1 from the UE 100.

[0057] In step S104, the BS 200 transmits a message 2 (hereinafter, MSG2) to the UE 100. MSG2 is a random access response. MSG2 includes a TA command for adjusting the transmission timing of the uplink signal. The TA command is, for example, N TAis the value. BS200 determines the TA command for UE100 according to the reception timing of MSG1. UE100 receives MSG2 from BS200.

[0058] In step S105, UE100 adjusts the uplink transmission timing based on the downlink frame timing. Specifically, UE100 advances the uplink frame timing used by UE100 by the time of (N TA +N TA,offset )T c .

[0059] In step S106, UE100 transmits message 3 (hereinafter, MSG3) to BS200. UE100 can transmit MSG3 at the adjusted uplink transmission timing in the initial BWP (specifically, the initial uplink BWP). BS200 receives MSG3 from UE100.

[0060] In step S107, BS200 transmits message 4 (hereinafter, MSG4) to UE100. UE100 receives MSG4 from BS200.

[0061] In step S108, the UE 100 communicates with the BS 200. For example, after receiving MSG4, the UE 100 may communicate with the BS 200 in an initial BWP determined based on the position and bandwidth in the frequency domain set using the information included in SIB1. Therefore, the UE 100 can communicate with the BS 200 with the initial BWP as the active BWP. For example, when the UE 100 communicates with the BS 200 using Time Division Duplex (TDD), the center frequency of the active downlink BWP and the center frequency of the active uplink BWP may be the same. When the UE 100 communicates with the BS 200 using Frequency Division Duplex (FDD), the center frequency of the active downlink BWP and the center frequency of the active uplink BWP may be the same or different. The bandwidth of the active downlink BWP and the bandwidth of the active uplink BWP may be the same or different. When the active uplink BWP and the active downlink BWP have the same center frequency, the active uplink BWP and the active downlink BWP correspond to each other.

[0062] The BS 200 may periodically notify the UE 100 of the TA command, or may notify it by an event trigger. The BS 200 may notify the UE 100 of the configuration information (for example, ServingCellConfigCommon) including N TA,offset (for example, n-TimingAdvanceOffset) to the UE 100 by an RRC message.

[0063] In addition, the BS 200 may transmit to the UE 100 the configuration information for setting an individual BWP using individual RRC signaling. After setting the individual BWP for the UE 100, the BS 200 may switch the active BWP to the individual BWP. The UE 100 may apply the parameters included in the configuration information and communicate with the BS 200 with the individual BWP as the active BWP.

[0064] Note that the configuration information may include at least any one of information indicating a position and a bandwidth in a frequency domain (e.g., locationAndBadwidth), information indicating a subcarrier spacing (e.g., subcarrierSpacing), information indicating whether to use an extended cyclic prefix (e.g., cyclicPrefix), information indicating parameters commonly applied to communication in an initial downlink BWP, and information indicating parameters commonly applied to communication in an initial uplink BWP. Further, the configuration information may include information for configuring an individual BWP (i.e., an individual downlink BWP and / or an individual uplink BWP). The information for configuring an individual BWP may include at least any one of information for identifying the BWP (e.g., bwp-id), information indicating parameters commonly applied to communication in the individual downlink BWP, information indicating parameters individually applied to communication in the individual downlink BWP, information indicating parameters commonly applied to communication in the individual uplink BWP, and information indicating parameters individually applied to communication in the individual uplink BWP.

[0065] The configuration information may include configuration information for measuring an SSB. The configuration information may include, as information indicating a measurement target, for example, information indicating a frequency at which the SSB is transmitted (e.g., an absolute radio frequency channel number (ARFCN), etc.).

[0066] In addition, when none of the multiple BWPs individually set for UE100 other than the initial BWP contains the frequency domain resources of the SSB associated with the initial BWP, BS200 may determine whether UE100 supports communication in the BWP where the SSB is not transmitted. For example, based on the capability information received from UE100, BS200 can determine whether UE100 supports communication in the BWP where the SSB is not transmitted. For example, when the capability information received from UE100 includes information indicating support for BWP operation without bandwidth restriction (e.g., bwp-WithoutRestriction), BS200 may determine that UE100 supports communication in the BWP where the SSB is not transmitted. In this case, BS200 may set the BWP where the SSB is not transmitted for UE100. Note that the bandwidth restriction means that, for example, the SSB may not be transmitted in the bandwidth of the downlink BWP individually set for UE100.

[0067] When BS200 determines that UE100 does not support communication in the BWP where the SSB is not transmitted, BS200 may always provide the setting of the measurement gap for the UE100. On the other hand, when BS200 determines that UE100 supports communication in the BWP where the SSB is not transmitted, BS200 may omit the setting of the measurement gap for the UE100.

[0068] For example, when BS200 periodically transmits the SSB in the active BWP, UE100 may periodically perform downlink timing synchronization in response to the reception of the SSB. UE100 may update the downlink frame timing maintained each time synchronization is performed.

[0069] In the following, assuming that a plurality of BWPs are set for UE100, the description will proceed. UE100 communicates with BS200 using one of the plurality of BWPs as the active BWP.

[0070] In step S109, BS200 transmits control information to UE100. UE100 receives the control information. The control information is information for switching the active BWP. BS200 may transmit the information for switching the active BWP to UE100 using individual RRC signaling or may transmit it using PDCCH.

[0071] In step S110, UE100 switches the active BWP. UE100 switches the active BWP based on the control information. When UE100 communicates with BS200 using TDD, the center frequency of the active downlink BWP is made to coincide with the center frequency of the active uplink BWP by switching the BWP. Also, when UE100 communicates with BS200 using FDD, the center frequency of the active downlink BWP may or may not be made to coincide with the center frequency of the active uplink BWP by switching the BWP.

[0072] In step S111, UE100 determines whether an SSB is being transmitted in the active BWP. Specifically, UE100 determines whether an SSB is being transmitted in the downlink BWP set as the active BWP (hereinafter, the active downlink BWP). That is, UE100 determines whether the active downlink BWP includes the SSB of the serving cell. If UE100 determines that an SSB is being transmitted in the active downlink BWP (YES), it executes the process of step S113. On the other hand, if UE100 determines that an SSB is not being transmitted in the active downlink BWP (NO), it performs the process of step S115. Note that step S111 may be performed before step S110.

[0073] For example, when the active downlink BWP is the initial BWP, the UE 100 determines that the SSB is being transmitted in the active downlink BWP. Note that the UE 100 can determine that the active downlink BWP is the initial BWP when the identifier of the configured active downlink BWP is 0. The UE 100 can determine that the active downlink BWP is not the initial BWP when the identifier of the configured active downlink BWP is other than 0. Also, for example, based on the information indicating the frequency at which the SSB is transmitted, the UE 100 may determine that the SSB is being transmitted in the active downlink BWP when the frequency at which the SSB is transmitted is included in the active downlink BWP. On the other hand, the UE 100 determines that the SSB is not being transmitted in the active downlink BWP when the frequency at which the SSB is transmitted is not included in the active downlink BWP.

[0074] In step S112, the BS 200 transmits the SSB to the UE 100 in a predetermined downlink BWP. The UE 100 receives the SSB when the BWP from which the SSB is transmitted by the BS 200 (hereinafter, appropriately referred to as the BWP with SSB) is the active downlink BWP. The UE 100 does not receive the SSB when the BWP from which the SSB is not transmitted by the BS 200 (hereinafter, appropriately referred to as the BWP without SSB) is the active downlink BWP. The UE 100 that has received the SSB in the active downlink BWP performs the process of step S113.

[0075] In step S113, the UE 100 performs downlink timing synchronization in the same manner as in step S102. The UE 100 maintains the downlink frame timing.

[0076] In step S114, UE100 adjusts the uplink transmission timing in the same manner as in step S105. Specifically, UE100 adjusts the uplink transmission timing based on the downlink frame timing held in step S113. Therefore, when the current active BWP is a BWP with SSB, UE100 adjusts the uplink transmission timing based on the downlink frame timing in the current active BWP, rather than based on the downlink frame timing held in the past active BWP.

[0077] In step S115, UE100 adjusts the uplink transmission timing based on the held downlink frame timing. Specifically, UE100 adjusts the uplink transmission timing based on the downlink frame timing used as a reference for adjusting the uplink transmission timing in step S108. Therefore, when the current active downlink BWP is a BWP without SSB, UE100 uses the downlink frame timing held in the past active downlink BWP as a reference for adjusting the uplink transmission timing.

[0078] In step S116, UE100 and BS200 communicate. UE100 performs uplink transmission at the adjusted uplink transmission timing. Specifically, when an SSB is being transmitted in the active BWP, that is, when the active BWP is a BWP with SSB, UE100 performs uplink transmission to BS200 at the uplink transmission timing adjusted by the process of step S114. On the other hand, when an SSB is not being transmitted in the active BWP, that is, when the active BWP is a BWP without SSB, UE100 performs uplink transmission to BS200 at the uplink transmission timing adjusted by the process of step S115.

[0079] As described above, the UE 100 (communication unit 110) communicates using the active BWP among the plurality of BWPs set in the UE 100 for communication with the BS 200. When the active BWP is a BWP with SSB, the UE 100 (control unit 120) holds the downlink frame timing in the BWP with SSB. When the active BWP is a BWP without SSB, the UE 100 (control unit 120) adjusts the uplink transmission timing in the active BWP based on the held downlink frame timing. Thereby, even when the BWP without SSB is the active BWP, the UE 100 can adjust the uplink transmission timing based on the held downlink frame timing, so that the uplink transmission timing can be appropriately adjusted.

[0080] Also, when the active BWP is a BWP with SSB, the UE 100 (control unit 120) adjusts the uplink transmission timing in the active BWP based on the downlink frame timing in the active BWP without using the held downlink frame timing as a reference. Thereby, when the UE 100 can grasp the downlink frame timing in the current active BWP, the uplink transmission timing can be appropriately adjusted by using this downlink frame timing as a reference.

[0081] (2.2) Operation Example 2 An operation example 2 of the UE 100 and the BS 200 according to the embodiment of the present disclosure will be described. The differences from the above-described content will be mainly described. In operation example 2, the UE 100 changes the downlink frame timing used as a reference for adjusting the uplink transmission timing according to whether the active BWP is the initial BWP.

[0082] Steps S201 to S210 correspond to steps S101 to S110.

[0083] In step S208, when the active BWP is the initial BWP, UE100 retains the downlink frame timing in the initial BWP. Even if an SSB is being transmitted in the active BWP, if the active BWP is not the initial BWP, UE100 does not have to retain the downlink frame timing in the active BWP. Therefore, UE100 may only retain the latest downlink frame timing in the initial BWP. Also, UE100 may update the downlink frame timing that is retained each time it synchronizes in the initial BWP. Even if UE100 synchronizes in a BWP other than the initial BWP, it does not have to update the retained downlink frame timing.

[0084] In step S211, UE100 determines whether the active BWP is the initial BWP. Specifically, UE100 can determine that the active BWP is the initial BWP when the identifier of the configured active BWP is 0. UE100 can determine that the active BWP is not the initial BWP when the identifier of the configured active BWP is other than 0.

[0085] If UE100 determines that the active BWP is the initial BWP (YES), it executes the process of step S213. On the other hand, if UE100 determines that the active BWP is not the initial BWP (NO), it executes the process of step S215.

[0086] Steps S212 to S216 correspond to steps S112 to S116. In step S215, UE100 adjusts the uplink transmission timing based on the downlink frame timing used as a reference for adjusting the uplink transmission timing in step S208. Therefore, when the current active downlink BWP is the initial BWP, UE100 uses the downlink frame timing retained in the past active downlink BWP as a reference for adjusting the uplink transmission timing.

[0087] Also, in step S216, when the active BWP is the initial BWP, the UE 100 performs an uplink transmission to the BS 200 at the uplink transmission timing adjusted by the process of step S214. On the other hand, when the active BWP is a BWP other than the initial BWP, the UE 100 performs an uplink transmission to the BS 200 at the uplink transmission timing adjusted by the process of step S215. Therefore, regardless of whether the SSB is being transmitted in the active downlink BWP, the UE 100 adjusts the uplink transmission timing based on the downlink frame timing in the initial BWP. That is, whenever the active downlink BWP is a BWP other than the initial downlink BWP 、 up uses the downlink frame timing in the initial downlink BWP including the SSB as a reference for adjusting the uplink transmission timing. Therefore, even if the SSB was being transmitted in the active downlink BWP, if the active downlink BWP is not the initial BWP, the UE 100 uses the downlink frame timing in the initial downlink BWP instead of using the downlink frame timing in the active downlink BWP as a reference.

[0088] As described above, the UE 100 (control unit 120) holds the downlink frame timing in the initial BWP when the active BWP is the initial BWP. When the active BWP is a BWP other than the initial BWP, the UE 100 (control unit 120) adjusts the uplink transmission timing based on the held downlink frame timing regardless of whether the SSB is being transmitted in the active BWP. When the UE 100 performs an uplink transmission in a BWP other than the initial BWP, without returning to the initial BWP, the UE 100 can adjust the uplink transmission timing using the reference of the downlink frame timing of the initial BWP held by the UE 100. Thereby, the load on the UE 100 can be reduced.

[0089] (Other Embodiments) In the above, embodiments of the present disclosure have been described, but the present disclosure is not limited to the embodiments. When the UE100 is a RedCap UE having the ability to support BWP operations without bandwidth limitation, the above-described operation example 1 and / or operation example 2 may be executed.

[0090] Moreover, each of the above-described operation examples is not limited to being implemented separately and independently, and each operation example can be implemented by appropriately combining them. Also, for example, the steps in the processes described in this specification do not necessarily have to be executed in time series in the order described in the flowchart or sequence diagram. For example, the steps in the process may be executed in an order different from the order described as a flowchart or sequence diagram, or may be executed in parallel. Also, some of the steps in the process may be deleted, and additional steps may be added to the process.

[0091] For example, a method including operations of one or more components of the apparatuses described in this specification may be provided, and a program for causing a computer to execute the operations of the above components may be provided. Also, a non-transitory tangible computer-readable storage medium recording the program may be provided. Such a method, program, and non-transitory tangible computer-readable storage medium are also included in the present disclosure. Also, at least a part of the UE100 or at least a part of the BS200 may be a chipset or SoC (System on Chip) in which circuits for executing each process performed by the UE100 or BS200 are integrated.

[0092] In the present disclosure, "transmit" may mean performing processing of at least one layer in a protocol stack used for transmission, or may mean physically transmitting a signal wirelessly or by wire. Alternatively, "transmit" may mean a combination of performing the processing of the at least one layer and physically transmitting a signal wirelessly or by wire. Similarly, "receive" may mean performing processing of at least one layer in a protocol stack used for reception, or may mean physically receiving a signal wirelessly or by wire. Alternatively, "receive" may mean a combination of performing the processing of the at least one layer and physically receiving a signal wirelessly or by wire.

[0093] As described above, embodiments of the present disclosure have been explained, but the present disclosure is not limited to the embodiments. It will be understood by those skilled in the art that the embodiments are merely illustrative and that various modifications can be made without departing from the scope and spirit of the present disclosure.

Explanation of Reference Numerals

[0094] 1: System 100: User Equipment (UE) 110: Communication Unit 120: Control Unit 200: Base Station (BS) 210: Communication Unit 212: Wireless Communication Unit 214: Network Communication Unit 220: Control Unit

Claims

A receiver that receives a radio resource control (RRC) message from a base station, the RRC message including information for setting a downlink BWP, the information including information indicating a downlink BWP, information indicating individual parameters used in the downlink BWP, information indicating transmission of a synchronization signal and a physical broadcast channel block (SSB) on the downlink BWP, and setting information for measurement of the SSB transmitted on the downlink BWP. A control unit that, when the downlink BWP set using the information for setting the downlink BWP is activated, performs measurement of the SSB indicated by using the information indicating transmission of the SSB based on the setting information for measurement of the SSB. When the downlink BWP set using the information for setting the downlink BWP is activated, the control unit determines downlink frame timing of a reference cell based on the SSB indicated by using the information indicating transmission of the SSB, and adjusts timing of uplink transmission based on the downlink frame timing. A communication device. The information for setting the downlink BWP includes information indicating a frequency domain position and a bandwidth of the downlink BWP. The information indicating transmission of the SSB includes an absolute radio frequency channel number of the SSB. Transmission of the SSB is indicated by the information indicating transmission of the SSB such that the SSB is transmitted in the bandwidth of the downlink BWP set based on the information indicating the frequency domain position and the bandwidth. The communication device according to claim 1.

3. The uplink transmission is transmission for a physical uplink shared channel. The communication device according to claim 1 or 2.

4. The information indicating the downlink BWP includes an identifier of the downlink BWP. The communication device according to claim 1 or 2.

5. A transmitter that performs the uplink transmission on an activated uplink BWP. The RRC message includes an identifier indicating an uplink BWP used as the uplink BWP. The communication device according to claim 1 or 2. A transmitter that transmits to a communication device a radio resource control (RRC) message including information for setting a downlink BWP, which includes information indicating the downlink BWP, information indicating individual parameters used in the downlink BWP, information indicating transmission of a synchronization signal and a physical broadcast channel block (SSB) on the downlink BWP, and setting information for measurement of the SSB transmitted on the downlink BWP. A receiver that receives a measurement result of the SSB indicated by using information indicating transmission of the SSB measured based on the setting information for measurement of the SSB when the downlink BWP set by using the information for setting the downlink BWP is activated. The receiver receives, from the communication device, an uplink signal whose transmission timing is adjusted based on the downlink frame timing of a reference cell determined based on the SSB indicated by using the information indicating transmission of the SSB when the downlink BWP set by using the information for setting the downlink BWP is activated. Base station. According to claim 6, the information for setting the downlink BWP includes information indicating the frequency domain position and bandwidth of the downlink BWP. The information indicating transmission of the SSB includes the absolute radio frequency channel number of the SSB. The transmission of the SSB is indicated by the information indicating transmission of the SSB such that the SSB is transmitted in the bandwidth of the downlink BWP set based on the information indicating the frequency domain position and bandwidth. The base station according to claim 6. According to claim 8 The transmission of the uplink signal is transmission to a physical uplink shared channel. The base station according to claim 6 or 7. According to claim 9 The information indicating the downlink BWP includes an identifier of the downlink BWP. The base station according to claim 6 or 7. According to claim 10 The receiver receives the uplink signal from the communication device on the uplink BWP that has been activated. The RRC message includes an identifier indicating the uplink BWP to be used as the uplink BWP. The base station according to claim 6 or 7. According to claim 11 A communication method executed by a communication device, Receiving, from a base station, a radio resource control (RRC) message including information for setting a downlink BWP, which includes information indicating a downlink BWP, information indicating individual parameters used in the downlink BWP, information indicating transmission of a synchronization signal and a physical broadcast channel block (SSB) on the downlink BWP, and setting information for measurement of the SSB transmitted on the downlink BWP; When the downlink BWP set using the information for setting the downlink BWP is activated, performing measurement of the SSB indicated by using the information indicating transmission of the SSB based on the setting information for measurement of the SSB; When the downlink BWP set using the information for setting the downlink BWP is activated, determining downlink frame timing of a reference cell based on the SSB indicated by using the information indicating transmission of the SSB, and adjusting timing of uplink transmission based on the downlink frame timing. A communication method.

12. The information for setting the downlink BWP includes information indicating a frequency domain position and a bandwidth of the downlink BWP. The information indicating transmission of the SSB includes an absolute radio frequency channel of the SSB. Transmission of the SSB is indicated by the information indicating transmission of the SSB such that the SSB is transmitted in the bandwidth of the downlink BWP set based on the information indicating the frequency domain position and the bandwidth. The communication method according to claim 11.

13. The uplink transmission is transmission on a physical uplink shared channel. The communication method according to claim 11 or 12.

14. The information indicating the downlink BWP includes an identifier of the downlink BWP. The communication method according to claim 11 or 12.

15. Comprising the step of performing the uplink transmission on an activated uplink BWP, The RRC message includes an identifier indicating an uplink BWP used as the uplink BWP. The communication method according to claim 11 or 12.

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