Communication terminal, base station, and communication system

Abstract

To provide technique that can prevent mismatch between the transmission timing of a communication terminal and the reception timing of a base station in uplink transmission before and after BWP switching.SOLUTION: A communication system includes a base station and a communication terminal configured to be able to wirelessly communicate with the base station. The communication terminal notifies the base station of information related to a switching time of a BWP (Bandwidth Part). The switching time of the BWP is determined for each numerology.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] The present invention relates to wireless communication technology.

Background Art

[0002] In the 3GPP (3rd Generation Partnership Project), which is a standardization organization for mobile communication systems, the radio section is called Long Term Evolution (LTE), and for the overall system configuration including the core network and the radio access network (hereinafter collectively referred to as the network), a communication method called System Architecture Evolution (SAE) is being studied (for example, Non-Patent Documents 1 to 5). This communication method is also called a 3.9G (3.9 Generation) system.

[0003] As the access method of LTE, OFDM (Orthogonal Frequency Division Multiplexing) is used in the downlink direction, and SC-FDMA (Single Carrier Frequency Division Multiple Access) is used in the uplink direction. Also, different from W-CDMA (Wideband Code Division Multiple Access), LTE does not include circuit switching and is only a packet communication method.

[0004] Regarding the decisions on the frame configuration in the LTE system in 3GPP described in Non-Patent Document 1 (Chapter 5), it will be described with reference to FIG. 1. FIG. 1 is an explanatory diagram showing the configuration of a radio frame used in a communication system of the LTE method. In FIG. 1, one radio frame is 10 ms. The radio frame is divided into 10 subframes of equal size. The subframe is divided into two slots of equal size. The downlink synchronization signal is included in the first and sixth subframes for each radio frame. The synchronization signal includes a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS).

[0005] The decisions on the channel configuration in the LTE system in 3GPP are described in Non-Patent Document 1 (Chapter 5). It is assumed that the same channel configuration as that of a non-CSG cell is used even in a CSG (Closed Subscriber Group) cell.

[0006] The physical broadcast channel (PBCH) is a channel for downlink transmission from a base station device (hereinafter sometimes simply referred to as "base station") to a communication terminal device such as a mobile terminal device (hereinafter sometimes simply referred to as "mobile terminal") (hereinafter sometimes simply referred to as "communication terminal"). The BCH transport block is mapped to 4 subframes during a 40-ms interval. There is no explicit signaling of the 40-ms timing.

[0007] The Physical Control Format Indicator Channel (PCFICH) is a channel for downlink transmission from a base station to a communication terminal. The PCFICH notifies the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols used for PDCCHs from the base station to the communication terminal. The PCFICH is transmitted for each subframe.

[0008] The Physical Downlink Control Channel (PDCCH) is a channel for downlink transmission from a base station to a communication terminal. The PDCCH notifies resource allocation information of the Downlink Shared Channel (DL-SCH), which is one of the transport channels described later, resource allocation information of the Paging Channel (PCH), which is one of the transport channels described later, and HARQ (Hybrid Automatic Repeat reQuest) information related to the DL-SCH. The PDCCH carries an Uplink Scheduling Grant. The PDCCH carries an Ack (Acknowledgement) / Nack (Negative Acknowledgement), which is a response signal for uplink transmission. The PDCCH is also called an L1 / L2 control signal.

[0009] The Physical Downlink Shared Channel (PDSCH) is a channel for downlink transmission from a base station to a communication terminal. The DL-SCH, which is a transport channel, and the PCH, which is a transport channel, are mapped to the PDSCH.

[0010] The Physical Multicast Channel (PMCH) is a channel for downlink transmission from a base station to a communication terminal. The Multicast Channel (MCH), which is a transport channel, is mapped to the PMCH.

[0011] The Physical Uplink Control Channel (PUCCH) is a channel for uplink transmission from a communication terminal to a base station. The PUCCH carries the Ack / Nack, which is a response signal for downlink transmission. The PUCCH carries the CSI (Channel State Information). The CSI is composed of the RI (Rank Indicator), PMI (Precoding Matrix Indicator), and CQI (Channel Quality Indicator) reports. The RI is the rank information of the channel matrix in MIMO. The PMI is the information of the precoding weight matrix used in MIMO. The CQI is the quality information indicating the quality of the received data or the channel quality. Also, the PUCCH carries the Scheduling Request (SR).

[0012] The Physical Uplink Shared Channel (PUSCH) is a channel for uplink transmission from a communication terminal to a base station. The Uplink Shared Channel (UL-SCH), which is one of the transport channels, is mapped to the PUSCH.

[0013] The Physical Hybrid ARQ Indicator Channel (PHICH) is a downlink channel from the base station to the communication terminal. The PHICH carries the Ack / Nack, which is a response signal for the uplink transmission. The Physical Random Access Channel (PRACH) is an uplink channel from the communication terminal to the base station. The PRACH carries the random access preamble.

[0014] The downlink reference signal (Reference Signal: RS) is a symbol known in the LTE communication system. The following five types of downlink reference signals are defined. The Cell-specific Reference Signal (CRS), the MBSFN Reference Signal, the Demodulation Reference Signal (DM-RS) which is the UE-specific Reference Signal, the Positioning Reference Signal (PRS), and the Channel State Information Reference Signal (CSI-RS). As a measurement of the physical layer of the communication terminal, there is the measurement of the Reference Signal Received Power (RSRP) of the reference signal.

[0015] Similarly, for the uplink reference signal, it is a symbol known in the LTE communication system. The following two types of uplink reference signals are defined. The Demodulation Reference Signal (DM-RS) and the Sounding Reference Signal (SRS).

[0016] The transport channel described in Non-Patent Document 1 (Chapter 5) will be explained. Among the downlink transport channels, the broadcast channel (BCH) is broadcast throughout the coverage area of its base station (cell). The BCH is mapped to the physical broadcast channel (PBCH).

[0017] For the downlink shared channel (DL-SCH), retransmission control by hybrid automatic repeat request (HARQ) is applied. The DL-SCH can be broadcast throughout the coverage area of the base station (cell). The DL-SCH supports dynamic or semi-static resource allocation. Semi-static resource allocation is also called persistent scheduling. The DL-SCH supports discontinuous reception (DRX) of the communication terminal for power consumption reduction of the communication terminal. The DL-SCH is mapped to the physical downlink shared channel (PDSCH).

[0018] The paging channel (PCH) supports DRX of the communication terminal to enable low power consumption of the communication terminal. The PCH requires broadcast throughout the coverage area of the base station (cell). The PCH is mapped to a physical resource such as the physical downlink shared channel (PDSCH) that can be dynamically used for traffic.

[0019] The multicast channel (MCH) is used for broadcast throughout the coverage area of the base station (cell). The MCH supports single-frequency network (SFN) combining of the multimedia broadcast multicast service (MTCH and MCCH) in multi-cell transmission. The MCH supports semi-static resource allocation. The MCH is mapped to the physical multicast channel (PMCH).

[0020] Among the uplink transport channels, for the uplink shared channel (UL-SCH), hybrid automatic repeat request (HARQ) retransmission control is applied. UL-SCH supports dynamic or semi-static resource allocation. UL-SCH is mapped to the physical uplink shared channel (PUSCH).

[0021] The random access channel (RACH) is limited to control information. RACH has a risk of collision. RACH is mapped to the physical random access channel (PRACH).

[0022] An explanation of HARQ is as follows. HARQ is a technology that improves the communication quality of the transmission path by combining automatic repeat request (ARQ) and forward error correction. HARQ has the advantage that error correction functions effectively by retransmission even for a transmission path where the communication quality changes. In particular, it is also possible to obtain further quality improvement by combining the reception result of the first transmission and the reception result of the retransmission during retransmission.

[0023] An example of the retransmission method is explained. At the receiving side, if the received data cannot be correctly decoded, in other words, if a cyclic redundancy check (CRC) error occurs (CRC = NG), the receiving side sends a "Nack" to the transmitting side. The transmitting side that receives the "Nack" retransmits the data. At the receiving side, if the received data can be correctly decoded, in other words, if no CRC error occurs (CRC = OK), the receiving side sends an "Ack" to the transmitting side. The transmitting side that receives the "Ack" transmits the next data.

[0024] The logical channel (Logical channel) described in Non-Patent Document 1 (Chapter 6) will be explained. The Broadcast Control Channel (BCCH) is a downlink channel for broadcast system control information. The BCCH, which is a logical channel, is mapped to the Broadcast Channel (BCH), which is a transport channel, or the Downlink Shared Channel (DL-SCH).

[0025] The Paging Control Channel (PCCH) is a downlink channel for transmitting paging information and changes in system information. The PCCH is used when the network does not know the cell location of the communication terminal. The PCCH, which is a logical channel, is mapped to the Paging Channel (PCH), which is a transport channel.

[0026] The Common Control Channel (CCCH) is a channel for transmission control information between a communication terminal and a base station. The CCCH is used when the communication terminal does not have an RRC connection with the network. In the downlink direction, the CCCH is mapped to the Downlink Shared Channel (DL-SCH), which is a transport channel. In the uplink direction, the CCCH is mapped to the Uplink Shared Channel (UL-SCH), which is a transport channel.

[0027] The Multicast Control Channel (MCCH) is a downlink channel for one-to-many transmission. The MCCH is used for transmitting MBMS control information for one or several MTCHs from the network to the communication terminal. The MCCH is used only for communication terminals receiving MBMS. The MCCH is mapped to the Multicast Channel (MCH), which is a transport channel.

[0028] The Dedicated Control Channel (DCCH) is a channel that transmits dedicated control information between a communication terminal and a network on a one-to-one basis. The DCCH is used when the communication terminal has an RRC connection. The DCCH is mapped to the UL-SCH in the uplink and to the DL-SCH in the downlink.

[0029] The Dedicated Traffic Channel (DTCH) is a channel for one-to-one communication to an individual communication terminal for the transmission of user information. The DTCH exists in both the uplink and the downlink. The DTCH is mapped to the UL-SCH in the uplink and to the DL-SCH in the downlink.

[0030] The Multicast Traffic channel (MTCH) is a downlink channel for the transmission of traffic data from the network to a communication terminal. The MTCH is a channel used only by communication terminals during MBMS reception. The MTCH is mapped to the Multicast Channel (MCH).

[0031] CGI stands for Cell Global Identifier. ECGI stands for E-UTRAN Cell Global Identifier. In LTE, the later LTE-A (Long Term Evolution Advanced), and UMTS (Universal Mobile Telecommunication System), Closed Subscriber Group (CSG) cells are introduced.

[0032] The location tracking of a communication terminal is performed in units of an area composed of one or more cells. The location tracking is performed to track the location of the communication terminal even in the standby state and to enable the calling of the communication terminal, in other words, to enable the communication terminal to receive an incoming call. The area for this location tracking of the communication terminal is called a tracking area.

[0033] Also, in 3GPP, as Release 10, the standardization of Long Term Evolution Advanced (LTE-A) is underway (see Non-Patent Document 3 and Non-Patent Document 4). LTE-A is based on the radio interval communication method of LTE and is configured by adding several new technologies thereto.

[0034] In the LTE-A system, in order to support a wider frequency bandwidth (transmission bandwidths) up to 100 MHz, carrier aggregation (CA) is being considered, which aggregates (also referred to as "aggregating") two or more component carriers (CCs). CA is described in Non-Patent Document 1.

[0035] When CA is configured, the UE has only one RRC connection with the network (NW). In the RRC connection, one serving cell provides NAS mobility information and security input. This cell is called the primary cell (PCell). In the downlink, the carrier corresponding to the PCell is the downlink primary component carrier (DL PCC). In the uplink, the carrier corresponding to the PCell is the uplink primary component carrier (UL PCC).

[0036] According to the capabilities of the UE, a Secondary Cell (SCell) is configured to form a set of serving cells together with the PCell. In the downlink, the carrier corresponding to the SCell is the Downlink Secondary Component Carrier (DL SCC). In the uplink, the carrier corresponding to the SCell is the Uplink Secondary Component Carrier (UL SCC).

[0037] A set of serving cells consisting of one PCell and one or more SCells is configured for one UE.

[0038] Also, as new technologies in LTE-A, there are technologies such as Wider bandwidth extension and Coordinated Multiple Point transmission and reception (CoMP). Regarding CoMP being studied for LTE-A by 3GPP, it is described in Non-Patent Document 1.

[0039] Also, in 3GPP, in order to cope with future huge traffic, it is being studied to use small eNBs (hereinafter sometimes referred to as "small base station devices") that constitute small cells. For example, technologies such as increasing the frequency utilization efficiency and increasing the communication capacity by installing a large number of small eNBs to form a large number of small cells are being studied. Specifically, there is Dual Connectivity (abbreviated as DC) where the UE connects to two eNBs to communicate. DC is described in Non-Patent Document 1.

[0040] Among the eNBs that perform dual connectivity (DC), one may be referred to as the "master eNB (abbreviated as MeNB)", and the other may be referred to as the "secondary eNB (abbreviated as SeNB)".

[0041] The traffic volume of mobile networks is on an increasing trend, and the communication speed is also accelerating. When LTE and LTE-A are fully launched into operation, it is expected that the communication speed will be further increased.

[0042] Furthermore, for advanced mobile communications, a fifth-generation (hereinafter sometimes referred to as "5G") radio access system with the goal of starting services after 2020 is being studied. For example, in Europe, the requirements for 5G have been summarized by a group called METIS (see Non-Patent Document 5).

[0043] In the 5G radio access system, compared with the LTE system, the system capacity is 1000 times, the data transmission speed is 100 times, the data processing delay is one-tenth (1 / 10), and the number of simultaneously connected communication terminals is 100 times. Further reduction of power consumption and cost of devices are listed as requirements.

[0044] To meet such requirements, in 3GPP, the standard study of 5G is being advanced as Release 15 (see Non-Patent Documents 6 to 18). The technology of the 5G radio section is called "New Radio Access Technology" (abbreviated as "NR" for "New Radio").

[0045] The NR system is being studied based on the LTE system and the LTE-A system, but changes and additions from the LTE system and the LTE-A system are being made in the following aspects.

[0046] As the access method of NR, OFDM is used in the downlink direction, and OFDM and DFT-s-OFDM (DFT-spread-OFDM) are used in the uplink direction.

[0047] In NR, in order to improve the transmission speed and reduce the processing delay, it is possible to use higher frequencies compared to LTE.

[0048] In NR, by forming a narrow beam-like transmission and reception range (beamforming) and changing the direction of the beam (beam sweeping), cell coverage is ensured.

[0049] In the frame structure of NR, various subcarrier intervals, that is, various numerologies are supported. In NR, regardless of the numerology, one subframe is 1 millisecond, and one slot is composed of 14 symbols. Also, the number of slots included in one subframe is one in the numerology with a subcarrier interval of 15 kHz, and in other numerologies, it increases in proportion to the subcarrier interval (see Non-Patent Document 13 (TS38.211 v15.0.0)).

[0050] The downlink synchronization signal in NR is transmitted from the base station at a predetermined period and with a predetermined duration as a Synchronization Signal Burst (hereinafter sometimes referred to as an SS burst). The SS burst is composed of Synchronization Signal Blocks (hereinafter sometimes referred to as SS blocks) for each beam of the base station. The base station transmits the SS blocks of each beam within the duration of the SS burst while changing the beam. The SS block is composed of P-SS, S-SS, and PBCH.

[0051] In NR, as a downlink reference signal in NR, by adding a Phase Tracking Reference Signal (PTRS), the influence of phase noise is reduced. Also, in the uplink reference signal, PTRS is added in the same way as in the downlink.

[0052] In NR, in order to flexibly perform DL / UL switching within a slot, Slot Format Indication (SFI) is added to the information included in the PDCCH.

[0053] Also, in NR, the base station pre-sets a part of the carrier frequency band (hereinafter sometimes referred to as Bandwidth Part (BWP)) for the UE, and the UE performs transmission and reception with the base station in the BWP, thereby reducing the power consumption of the UE.

[0054] In 3GPP, as DC configurations, DC using an LTE base station connected to the EPC and an NR base station, DC using an NR base station connected to the 5G core system, and DC using an LTE base station and an NR base station connected to the 5G core system are being studied (see Non-Patent Documents 12, 16, and 23).

[0055] Also, in 3GPP, several new technologies are being studied. For example, coexistence of NR communication and LTE communication at the same frequency in DC using an NR base station and an LTE base station (hereinafter sometimes referred to as NR-LTE coexistence), and reduction of UE power consumption by using BWP (Bandwidth Part) are being studied (see Non-Patent Documents 19 to 22).

[0056] In NR, the SRS used for uplink channel sounding is allocated within the range of the last 6 symbols of 1 slot composed of 14 symbols. Also, the number of symbols of the SRS is either 1, 2, or 4 (see Non-Patent Documents 13 and 15).

Prior Art Documents

Non-Patent Documents

[0057]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Non-Patent Document 8

Non-Patent Document 9

Non-Patent Document 10

Non-Patent Document 11

Non-Patent Document 12

Non-Patent Document 13

Non-Patent Document 14

Non-Patent Document 15

Non-Patent Document 16

Non-Patent Document 17

Non-Patent Document 18

Non-Patent Document 19

Non-Patent Document 20

Non-Patent Document 21

Non-Patent Document 22

Non-Patent Document 23

Summary of the Invention

Problems to be Solved by the Invention

[0058] In NR-LTE coexistence, the NR base station notifies the LTE base station of information regarding the slots scheduled by the NR base station. However, in the NR system, since different numerologies are supported, the LTE base station cannot grasp the timing of the slots scheduled by the NR base station. Therefore, in NR-LTE coexistence, there is a possibility that the NR base station and the LTE base station perform scheduling for the same timing. As a result, the UE becomes unable to communicate with one of the base stations, and consequently, there arises a problem that the reliability and transmission rate in the communication between the UE and the base station decrease.

[0059]

[0060] In NR, in order to reduce the power consumption of the UE, the use of a BWP that uses a part of the UL carrier band is being considered. However, when the UE switches the BWP and performs uplink transmission, the time required for BWP switching is not taken into consideration. Therefore, in the base station, uplink scheduling near the time of BWP switching is not appropriately performed, and as a result, there occur problems of a decrease in the reliability of uplink communication and a decrease in the uplink transmission rate at the time of BWP switching.

Means for Solving the Problems

[0061] ​ The communication terminal according to the present invention is a communication terminal configured to be capable of wireless communication with a base station, wherein the communication terminal notifies the base station of information regarding the switching time of a BWP (Bandwidth Part), and the switching time is determined for each numerology.

[0062] Further, the base station according to the present invention is a base station configured to be capable of wireless communication with a communication terminal, wherein the base station receives information regarding the switching time of a BWP (Bandwidth Part) from the communication terminal, the switching time is determined for each numerology, and scheduling is performed for the communication terminal based on the information regarding the switching time.

[0063] The communication system according to the present invention includes a base station and a communication terminal configured to be capable of wireless communication with the base station, wherein the communication terminal notifies the base station of information regarding the switching time of a BWP (Bandwidth Part), and the switching time is determined for each numerology.

Advantages of the Invention

[0064] According to the present invention, it is possible to prevent a mismatch between the transmission timing of the communication terminal and the reception timing of the base station in the uplink transmission before and after BWP switching. As a result, it is possible to ensure the reliability and communication rate of communication.

[0065] The object, features, aspects, and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

Brief Description of the Drawings

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MODE FOR CARRYING OUT THE INVENTION

[0067] Embodiment 1. FIG. 2 is a block diagram showing the overall configuration of an LTE-based communication system 200 being discussed in 3GPP. FIG. 2 will be described. The radio access network is referred to as E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 201. A mobile terminal device (hereinafter simply referred to as "mobile terminal (User Equipment: UE)") 202, which is a communication terminal device, can communicate wirelessly with a base station device (hereinafter referred to as "base station (E-UTRAN NodeB: eNB)") 203 and perform signal transmission and reception through wireless communication.

[0068] Here, the "communication terminal device" includes not only mobile terminal devices such as mobile phone terminal devices that can move, but also non-mobile devices such as sensors. In the following description, the "communication terminal device" may sometimes be simply referred to as the "communication terminal".

[0069] If a control protocol for the mobile terminal 202, for example, RRC (Radio Resource Control), and a user plane (hereinafter, may also be referred to as U-Plane), for example, PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), and PHY (Physical layer) are terminated at the base station 203, then the E-UTRAN is composed of one or more base stations 203.

[0070] The control protocol RRC (Radio Resource Control) between the mobile terminal 202 and the base station 203 performs broadcast, paging, RRC connection management, etc. As the states of the base station 203 and the mobile terminal 202 in RRC, there are RRC_IDLE and RRC_CONNECTED.

[0071] In RRC_IDLE, PLMN (Public Land Mobile Network) selection, system information (SI) broadcast, paging, cell re-selection, mobility, etc. are performed. In RRC_CONNECTED, the mobile terminal has an RRC connection and can transmit and receive data with the network. Also, in RRC_CONNECTED, handover (HO), measurement of adjacent cells (neighbour cell measurement), etc. are performed.

[0072] The base station 203 is composed of one or more eNBs 207. A system composed of the core network EPC (Evolved Packet Core) and the radio access network E-UTRAN 201 is called EPS (Evolved Packet System). The combination of the core network EPC and the radio access network E-UTRAN 201 is sometimes referred to as the "network".

[0073] The eNB 207 is connected to the Mobility Management Entity (MME), or the Serving Gateway (S-GW), or the MME / S-GW unit (hereinafter sometimes referred to as the "MME unit") 204 including the MME and the S-GW through the S1 interface, and control information is communicated between the eNB 207 and the MME unit 204. A plurality of MME units 204 may be connected to one eNB 207. The eNBs 207 are connected through the X2 interface, and control information is communicated between the eNBs 207.

[0074] The MME unit 204 is a higher-level device, specifically a higher-level node, and controls the connection between the base station eNB 207 and the mobile terminal (UE) 202. The MME unit 204 constitutes the core network EPC. The base station 203 constitutes the E-UTRAN 201.

[0075] The base station 203 may constitute one cell or a plurality of cells. Each cell has a range predetermined as a coverage that is a range in which communication with the mobile terminal 202 is possible, and wireless communication is performed with the mobile terminal 202 within the coverage. When one base station 203 constitutes a plurality of cells, each cell is configured to be able to communicate with the mobile terminal 202.

[0076] FIG. 3 is a block diagram showing the overall configuration of a 5G communication system 210 being discussed in 3GPP. FIG. 3 will be described. The radio access network is referred to as NG-RAN (Next Generation Radio Access Network) 211. The UE 202 can communicate wirelessly with an NR base station device (hereinafter referred to as "NR base station (NG-RAN NodeB: gNB)") 213 and perform signal transmission and reception through wireless communication. Also, the core network is referred to as 5G Core (5GC).

[0077] If the control protocol for the UE 212, for example, RRC (Radio Resource Control), and the user plane (hereinafter sometimes referred to as U-Plane), for example, SDAP (Service Data Adaptation Protocol), PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), PHY (Physical layer) are terminated at the NR base station 213, the NG-RAN is composed of one or more NR base stations 213.

[0078] The function of the control protocol RRC (Radio Resource Control) between the UE 202 and the NR base station 213 is the same as that of LTE. As the states of the NR base station 213 and the UE 202 in RRC, there are RRC_IDLE, RRC_CONNECTED, and RRC_INACTIVE.

[0079] RRC_IDLE and RRC_CONNECTED are the same as in the LTE mode. RRC_INACTIVE performs system information (SI) notification, paging, cell re-selection, mobility, etc. while maintaining the connection between the 5G core and the NR base station 213.

[0080] gNB 217 is connected to an access and mobility management function (AMF), a session management function (SMF), or a UPF (user plane function), or an AMF / SMF / UPF unit (hereinafter sometimes referred to as the "5GC unit") 214 including AMF, SMF, and UPF, via an NG interface. Control information and / or user data are communicated between gNB 217 and the 5GC unit 214. The NG interface is a general term for the N2 interface between gNB 217 and the AMF, the N3 interface between gNB 217 and the UPF, the N11 interface between the AMF and the SMF, and the N4 interface between the UPF and the SMF. For one gNB 217, a plurality of 5GC units 204 may be connected. gNBs 217 are connected to each other via an Xn interface, and control information and / or user data are communicated between the gNBs 217.

[0081] Similar to the base station 203, the NR base station 213 may also constitute one or more cells. When one NR base station 213 constitutes a plurality of cells, each cell is configured to be able to communicate with the UE 212.

[0082] gNB 217 may be divided into a central unit (hereinafter sometimes referred to as CU) 218 and a distributed unit (hereinafter sometimes referred to as DU) 219. One CU 218 is configured in gNB 217. One or more DUs 219 are configured in gNB 217. The CU 218 is connected to the DU 219 via an F1 interface, and control information and / or user data are communicated between the CU 218 and the DU 219.

[0083] FIG. 4 is a diagram showing the configuration of DC by an eNB and a gNB connected to the EPC. In FIG. 4, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In FIG. 4, eNB 223-1 becomes the master base station, and gNB 224-2 becomes the secondary base station (this DC configuration may be referred to as EN-DC). In FIG. 4, an example is shown in which the U-Plane connection between the MME unit 204 and gNB 224-2 is made via eNB 223-1, but it may also be made directly between the MME unit 221 and gNB 224-2.

[0084] FIG. 5 is a diagram showing the configuration of DC by a gNB connected to the NG core. In FIG. 5, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In FIG. 5, gNB 224-1 becomes the master base station, and gNB 224-2 becomes the secondary base station (this DC configuration may be referred to as NR-DC). In FIG. 5, an example is shown in which the U-Plane connection between the 5GC unit 214 and gNB 224-2 is made via gNB 224-1, but it may also be made directly between the 5GC unit 214 and gNB 224-2.

[0085] FIG. 6 is a diagram showing the configuration of DC by an eNB and a gNB connected to the NG core. In FIG. 6, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In FIG. 6, eNB 226-1 becomes the master base station, and gNB 224-2 becomes the secondary base station (this DC configuration may be referred to as NG-EN-DC). In FIG. 6, an example is shown in which the U-Plane connection between the 5GC unit 214 and gNB 224-2 is made via eNB 226-1, but it may also be made directly between the 5GC unit 214 and gNB 224-2.

[0086] FIG. 7 is a diagram showing another configuration of DC by an eNB and a gNB connected to an NG core. In FIG. 7, solid lines indicate U-Plane connections, and dashed lines indicate C-Plane connections. In FIG. 7, gNB224-1 becomes the master base station, and eNB226-2 becomes the secondary base station (this DC configuration may be referred to as NE-DC). In FIG. 7, an example is shown in which the U-Plane connection between the 5GC unit 214 and eNB226-2 is made via gNB224-1, but it may be made directly between the 5GC unit 214 and eNB226-2.

[0087] FIG. 8 is a block diagram showing the configuration of the mobile terminal 202 shown in FIG. 2. The transmission process of the mobile terminal 202 shown in FIG. 8 will be described. First, the control data from the protocol processing unit 301 and the user data from the application unit 302 are stored in the transmission data buffer unit 303. The data stored in the transmission data buffer unit 303 is passed to the encoder unit 304, and encoding processing such as error correction is performed. There may be data that is directly output from the transmission data buffer unit 303 to the modulation unit 305 without undergoing encoding processing. The data encoded by the encoder unit 304 is subjected to modulation processing by the modulation unit 305. Precoding in MIMO may be performed by the modulation unit 305. The modulated data is converted into a baseband signal and then output to the frequency conversion unit 306, where it is converted to a radio transmission frequency. Thereafter, transmission signals are transmitted from the antennas 307-1 to 307-4 to the base station 203. In FIG. 8, the case where the number of antennas is four is illustrated as an example, but the number of antennas is not limited to four.

[0088] In addition, the reception process of the mobile terminal 202 is executed as follows. The radio signals from the base station 203 are received by the antennas 307-1 to 307-4. The received signals are converted from the radio reception frequency to baseband signals by the frequency conversion unit 306, and demodulation processing is performed by the demodulation unit 308. The demodulation unit 308 may perform weight calculation and multiplication processing. The demodulated data is passed to the decoder unit 309, and decoding processing such as error correction is performed. Among the decoded data, the control data is passed to the protocol processing unit 301, and the user data is passed to the application unit 302. A series of processes of the mobile terminal 202 are controlled by the control unit 310. Therefore, although omitted in FIG. 8, the control unit 310 is connected to each of the units 301 to 309. In FIG. 8, the number of antennas used for transmission and the number of antennas used for reception by the mobile terminal 202 may be the same or different.

[0089] FIG. 9 is a block diagram showing the configuration of the base station 203 shown in FIG. 2. The transmission process of the base station 203 shown in FIG. 9 will be described. The EPC communication unit 401 performs data transmission and reception between the base station 203 and the EPC (such as the MME unit 204), the HeNB GW 205, etc. The 5GC communication unit 412 performs data transmission and reception between the base station 203 and the 5GC (such as the 5GC unit 214). The other base station communication unit 402 performs data transmission and reception with other base stations. The EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402 each exchange information with the protocol processing unit 403. The control data from the protocol processing unit 403, as well as the user data and control data from the EPC communication unit 401, the 5GC communication unit 412, and the other base station communication unit 402, are stored in the transmission data buffer unit 404.

[0090] The data stored in the transmission data buffer unit 404 is passed to the encoder unit 405, and encoding processes such as error correction are performed. There may be data that is directly output from the transmission data buffer unit 404 to the modulation unit 406 without undergoing the encoding process. The encoded data is subjected to modulation processing in the modulation unit 406. Precoding in MIMO may be performed in the modulation unit 406. The modulated data is converted into a baseband signal and then output to the frequency conversion unit 407, where it is converted to a wireless transmission frequency. Thereafter, a transmission signal is transmitted from one or more of the antennas 408-1 to 408-4 to the mobile terminal 202. In FIG. 9, the case where the number of antennas is four is illustrated, but the number of antennas is not limited to four.

[0091] Also, the reception process of the base station 203 is executed as follows. A wireless signal from one or more mobile terminals 202 is received by the antenna 408. The received signal is converted from the wireless reception frequency to a baseband signal in the frequency conversion unit 407, and demodulation processing is performed in the demodulation unit 409. The demodulated data is passed to the decoder unit 410, and decoding processes such as error correction are performed. Among the decoded data, the control data is passed to the protocol processing unit 403, the EPC communication unit 401, or the other base station communication unit 402, and the user data is passed to the EPC communication unit 401 and the other base station communication unit 402. A series of processes of the base station 203 is controlled by the control unit 411. Therefore, although omitted in FIG. 4, the control unit 411 is connected to each of the units 401 to 410. In FIG. 9, the number of antennas used for transmission and the number of antennas used for reception by the base station 203 may be the same or different.

[0092] FIG. 9 is a block diagram showing the configuration of the base station 203, but the base station 213 may have a similar configuration. Also, regarding FIGS. 8 and 9, the number of antennas of the mobile terminal 202 and the number of antennas of the base station 203 may be the same or different.

[0093] FIG. 10 is a block diagram showing the configuration of the MME. In FIG. 10, the configuration of the MME 204a included in the MME unit 204 shown in FIG. 2 described above is shown. The PDN GW communication unit 501 transmits and receives data between the MME 204a and the PDN GW. The base station communication unit 502 transmits and receives data via the S1 interface between the MME 204a and the base station 203. When the data received from the PDN GW is user data, the user data is passed from the PDN GW communication unit 501 to the base station communication unit 502 via the user plain communication unit 503 and transmitted to one or more base stations 203. When the data received from the base station 203 is user data, the user data is passed from the base station communication unit 502 to the PDN GW communication unit 501 via the user plain communication unit 503 and transmitted to the PDN GW.

[0094] When the data received from the PDN GW is control data, the control data is passed from the PDN GW communication unit 501 to the control plain control unit 505. When the data received from the base station 203 is control data, the control data is passed from the base station communication unit 502 to the control plain control unit 505.

[0095] The HeNBGW communication unit 504 is provided when the HeNBGW 205 exists and transmits and receives data via the interface (IF) between the MME 204a and the HeNBGW 205 depending on the information type. The control data received from the HeNBGW communication unit 504 is passed from the HeNBGW communication unit 504 to the control plain control unit 505. The result of the processing in the control plain control unit 505 is transmitted to the PDN GW via the PDN GW communication unit 501. Also, the result processed in the control plain control unit 505 is transmitted to one or more base stations 203 via the base station communication unit 502 by the S1 interface and to one or more HeNBGWs 205 via the HeNBGW communication unit 504.

[0096] The control plane control unit 505 includes an NAS security unit 505-1, an SAE bearer control unit 505-2, an idle state mobility management unit 505-3, etc., and performs all processes for the control plane (hereinafter, may also be referred to as the C-Plane). The NAS security unit 505-1 performs security of NAS (Non-Access Stratum) messages, etc. The SAE bearer control unit 505-2 performs management of the bearers of SAE (System Architecture Evolution), etc. The idle state mobility management unit 505-3 performs mobility management in the standby state (idle state; LTE-IDLE state, or simply referred to as idle), generation and control of paging signals in the standby state, addition, deletion, update, search, and tracking area list management of one or more mobile terminals 202 under its umbrella.

[0097] The MME 204a distributes paging signals to one or more base stations 203. Also, the MME 204a performs mobility control in the idle state. The MME 204a manages the tracking area list when the mobile terminal is in the standby state and in the active state. The MME 204a initiates the paging protocol by transmitting a paging message to a cell belonging to the tracking area (tracking area) in which the UE is registered. The management of the CSG of the Home-eNB 206 connected to the MME 204a, the management of the CSG ID, and the management of the white list may be performed by the idle state mobility management unit 505-3.

[0098] FIG. 11 is a block diagram showing the configuration of 5GC. In FIG. 11, the configuration of the 5GC unit 214 shown in FIG. 3 described above is shown. FIG. 11 shows the case where the configuration of the AMF, the SMF, and the UPF is included in the 5GC unit 214 shown in FIG. 5. The Data Network communication unit 521 transmits and receives data between the 5GC unit 214 and the Data Network. The base station communication unit 522 transmits and receives data via the S1 interface between the 5GC unit 214 and the base station 203 and / or the NG interface between the 5GC unit 214 and the base station 213. When the data received from the Data Network is user data, the user data is passed from the Data Network communication unit 521 to the base station communication unit 522 via the user plain communication unit 523 and transmitted to one or more of the base stations 203 and / or the base station 213. When the data received from the base station 203 and / or the base station 213 is user data, the user data is passed from the base station communication unit 522 to the Data Network communication unit 521 via the user plain communication unit 523 and transmitted to the Data Network.

[0099] When the data received from the Data Network is control data, the control data is passed from the Data Network communication unit 521 to the session management unit 527. The session management unit 527 passes the control data to the control plane control unit 525. When the data received from the base station 203 and / or the base station 213 is control data, the control data is passed from the base station communication unit 522 to the control plane control unit 525. The control plane control unit 525 passes the control data to the session management unit 527.

[0100] The control plane control unit 525 includes a NAS security unit 525-1, a PDU session control unit 525-2, an idle state mobility management unit 525-3, etc., and performs all processes for the control plane (hereinafter, may also be referred to as the C-Plane). The NAS security unit 525-1 performs security of NAS (Non-Access Stratum) messages, etc. The PDU session control unit 525-2 performs management of PDU sessions between the mobile terminals 202 and the 5GC unit 214, etc. The idle state mobility management unit 525-3 performs mobility management in the standby state (idle state; RRC_IDLE state, or simply also referred to as idle), generation and control of paging signals in the standby state, addition, deletion, update, search of the tracking area of one or more mobile terminals 202 under its umbrella, tracking area list management, etc.

[0101] The 5GC unit 214 distributes paging signals to one or more base stations 203 and / or base station 213. Also, the 5GC unit 214 performs mobility control in the idle state. The 5GC unit 214 manages the tracking area list when the mobile terminal is in the inactive state and the active state when it is in the standby state. The 5GC unit 214 initiates the paging protocol by sending a paging message to the cell belonging to the tracking area (tracking area) where the UE is registered.

[0102] Next, an example of a cell search method in a communication system is shown. FIG. 12 is a flowchart showing an overview from cell search to standby operation performed by a communication terminal (UE) in an LTE communication system. When the communication terminal starts cell search, in step ST601, it synchronizes the slot timing and frame timing using the first synchronization signal (P-SS) and the second synchronization signal (S-SS) transmitted from surrounding base stations.

[0103] The P-SS and S-SS are combined and called the synchronization signal (SS). The synchronization signal (SS) is assigned a synchronization code that corresponds one-to-one to the PCI assigned to each cell. 504 types of PCI are being considered. Synchronization is performed using these 504 types of PCI, and the PCI of the synchronized cell is detected (identified).

[0104] Next, for the cell that has been synchronized, in step ST602, the cell-specific reference signal (CRS), which is a reference signal (reference signal: RS) transmitted from the base station for each cell, is detected, and the received power of the RS (reference signal received power: RSRP) is measured. A code corresponding one-to-one to the PCI is used for the reference signal (RS). By correlating with that code, it can be separated from other cells. By deriving the code for the RS of the cell from the PCI identified in step ST601, it becomes possible to detect the RS and measure the received power of the RS.

[0105] Next, in step ST603, from among the one or more cells detected up to step ST602, the cell with the best reception quality of the RS, for example, the cell with the highest received power of the RS, that is, the best cell, is selected.

[0106] Next, in step ST604, the PBCH of the best cell is received to obtain the BCCH which is the notification information. The MIB (Master Information Block) containing cell configuration information is mapped to the BCCH on the PBCH. Therefore, by receiving the PBCH and obtaining the BCCH, the MIB can be obtained. Examples of the information in the MIB include the DL (downlink) system bandwidth (also called transmission bandwidth configuration: dl - bandwidth), the number of transmission antennas, the SFN (System Frame Number), etc.

[0107] Next, in step ST605, based on the cell configuration information in the MIB, the DL - SCH of the cell is received to obtain the SIB (System Information Block) 1 in the notification information BCCH. The SIB1 contains information related to access to the cell, information related to cell selection, and scheduling information for other SIBs (SIBk; k is an integer greater than or equal to 2). Also, the SIB1 contains the Tracking Area Code (TAC).

[0108] Next, in step ST606, the communication terminal compares the TAC of the SIB1 received in step ST605 with the TAC part of the Tracking Area Identity (TAI) in the tracking area list that the communication terminal already possesses. The tracking area list is also referred to as the TAI list. The TAI is identification information for identifying a tracking area and is composed of an MCC (Mobile Country Code), an MNC (Mobile Network Code), and a TAC (Tracking Area Code). The MCC is the country code. The MNC is the network code. The TAC is the code number of the tracking area.

[0109] If, as a result of the comparison in step ST606, the TAC received in step ST605 is the same as the TAC included in the tracking area list, the communication terminal enters the standby operation in the cell. If, upon comparison, the TAC received in step ST605 is not included in the tracking area list, the communication terminal requests a change in the tracking area to perform a TAU (Tracking Area Update) to the core network (Core Network, EPC) including an MME or the like through the cell.

[0110] In the example shown in FIG. 12, an example of the operation from cell search to standby in the LTE system was shown. In the NR system, in step ST603, in addition to the best cell, the best beam may be selected. Also, in the NR system, in step ST604, beam information, for example, a beam identifier may be acquired. Also, in the NR system, in step ST604, scheduling information of the remaining minimum SI (Remaining Minimum SI: RMSI) may be acquired. In the NR system, in step ST605, it may be assumed that RMSI is received.

[0111] The device constituting the core network (hereinafter sometimes referred to as the "core network side device") updates the tracking area list based on the identification number (such as UE-ID) of the communication terminal sent from the communication terminal together with the TAU request signal. The core network side device transmits the updated tracking area list to the communication terminal. The communication terminal rewrites (updates) the TAC list held by the communication terminal based on the received tracking area list. Thereafter, the communication terminal enters the standby operation in the cell.

[0112] Due to the spread of smartphones and tablet-type terminal devices, traffic by cellular wireless communication has increased explosively, and a shortage of wireless resources is a concern worldwide. In response to this, in order to improve the frequency utilization efficiency, it is being considered to miniaturize cells and promote spatial separation.

[0113] In the configuration of conventional cells, a cell configured by an eNB has a relatively wide coverage area. Conventionally, cells have been configured to cover a certain area by the relatively wide coverage areas of a plurality of cells configured by a plurality of eNBs.

[0114] When small cells are formed, a cell configured by an eNB has a coverage area that is narrower than that of a cell configured by a conventional eNB. Therefore, in order to cover a certain area as in the conventional case, a larger number of small cell eNBs are required compared to conventional eNBs.

[0115] In the following description, a cell with a relatively large coverage area, such as a cell configured by a conventional eNB, is referred to as a "macro cell", and the eNB that configures the macro cell is referred to as a "macro eNB". Also, a cell with a relatively small coverage area, such as a small cell, is referred to as a "small cell", and the eNB that configures the small cell is referred to as a "small eNB".

[0116] The macro eNB may be, for example, a "Wide Area Base Station" described in Non-Patent Document 7.

[0117] The small eNB may be, for example, a low power node, a local area node, a hot spot, etc. Also, the small eNB may be a pico eNB that configures a pico cell, a femto eNB that configures a femto cell, a HeNB, an RRH (Remote Radio Head), an RRU (Remote Radio Unit), an RRE (Remote Radio Equipment), or an RN (Relay Node). Further, the small eNB may be a "Local Area Base Station" or a "Home Base Station" described in Non-Patent Document 7.

[0118] Figure 13 shows an example of the configuration of a cell in NR. In an NR cell, a narrow beam is formed and transmitted while changing the direction. In the example shown in Figure 13, at a certain time, the base station 750 communicates with the mobile terminal using beam 751-1. At other times, the base station 750 communicates with the mobile terminal using beam 751-2. Similarly hereinafter, the base station 750 communicates with the mobile terminal using one or more of beams 751-3 to 751-8. By doing so, the base station 750 constitutes a wide-area cell.

[0119] In Figure 13, an example where the number of beams used by the base station 750 is 8 is shown, but the number of beams may be different from 8. Also, in the example shown in Figure 13, the number of beams used by the base station 750 simultaneously is 1, but it may be more than one.

[0120] As a method of scheduling by an NR base station and an LTE base station in NR-LTE coexistence, the NR base station allocates a slot for communicating with the UE, and the LTE base station allocates a slot for communicating with the UE to the remaining slots after the allocation.

[0121] The NR base station may notify the LTE base station of information on the slots allocated by the own base station. For this notification, an interface between base stations may be used. Also, the NR base station may notify the LTE base station of information regarding frame timing. The LTE base station may use this information to obtain information regarding the difference between the frame timing in the NR base station and the frame timing in the LTE base station. The LTE base station may perform scheduling for the UE using the information obtained above.

[0122] The configuration of DC described above may be the configuration shown in Figure 4, or the configuration shown in Figure 6, or the configuration shown in Figure 7.

[0123] In the foregoing method, the following problems occur. That is, in the NR system, since different numerologies are supported, the LTE base station cannot grasp the time resources scheduled by the NR base station. Therefore, in NR-LTE coexistence, there is a possibility that the time resources scheduled by the NR base station and the LTE base station collide. As a result, the UE cannot communicate with one of the base stations, and thus there arises a problem that the reliability and transmission rate in the communication between the UE and the base station decrease.

[0124] A method for solving the foregoing problems is disclosed. The NR base station notifies the LTE base station of information regarding the numerology used in communication with the UE. The LTE base station uses this information to obtain information on the time resources scheduled by the NR base station.

[0125] The NR base station may include the information regarding the foregoing numerology in the information on the slot scheduled by the NR base station for the UE and notify it. The information on the foregoing slot may include information regarding the scheduled symbol. Thereby, for example, the LTE base station can obtain information on the time resources scheduled by the NR base station in one signaling. Therefore, in NR-LTE coexistence, the LTE base station can perform rapid scheduling processing.

[0126] As another example, the NR base station may notify the information related to the numerology described above by including it in the information related to the frame timing of its own NR base station. The information related to the frame timing described above may be, for example, information related to the frame boundary, information related to the frame number, or information related to the difference in frame timing between the NR base station and the LTE base station. The difference may be measured by the NR base station receiving and measuring the downlink signal of the LTE base station, or may be measured by the UE and notified to the NR base station. This makes it possible to reduce, for example, the number of transmissions of the information related to the numerology transmitted from the NR base station to the LTE base station. As a result, it is possible to reduce the amount of signaling in the interface between base stations.

[0127] As another example, the NR base station may notify the LTE base station without including the information related to the numerology described above in either the information of the slot scheduled by its own NR base station or the information of the frame timing of its own NR base station. For example, the NR base station may notify the information related to the numerology described above to the LTE base station using signaling that notifies only this information. The signaling described above may be newly provided. Alternatively, the NR base station may notify the information by including it in other information. For example, the NR base station may notify the information by including it in the signaling that notifies the LTE base station of the RRC configuration change of the UE. This makes it possible to flexibly change the numerology used for transmission and reception between the NR base station and the UE, and at the same time reduce the amount of signaling from the NR base station to the LTE base station.

[0128] FIG. 14 is a diagram showing the operation of the NR base station notifying the LTE base station of the information on the numerology used in the communication with the UE. FIG. 14 shows the case where the NR base station notifies the information by including it in the information of the slot assigned by its own base station.

[0129] In step ST1501 shown in FIG. 14, the NR base station notifies the numerology information used in communication with the UE by including it in the information of the slot allocated by the self-NR base station to the UE. In step ST1502, the same operation as in step ST1501 is performed. The above-mentioned step ST1502 is performed when the information of the slot allocation in step ST1501 is updated. Step ST1502 may also be performed when the numerology used in communication with the UE is changed.

[0130] FIG. 15 is a diagram showing another example of the operation in which the NR base station notifies the LTE base station of the numerology information used in communication with the UE. FIG. 15 shows the case where the NR base station notifies the information by including it in the information of the frame timing of the self-base station.

[0131] In step ST1601 shown in FIG. 15, the NR base station notifies the numerology information used in communication with the UE by including it in the information of the frame timing used by the self-base station. In step ST1602, the NR base station notifies the LTE base station of the information of the slot allocated by the self-NR base station to the UE. The LTE base station derives the time resources allocated by the NR base station using the information of the above-mentioned ST1601 and ST1602. In step ST1603 as well, the NR base station performs the same operation as in step ST1602. The LTE base station derives the time resources allocated by the NR base station using the information of the above-mentioned ST1601 and ST1603.

[0132] In the first embodiment, although the NR base station notifies the LTE base station of information regarding numerology, the UE may notify information regarding the BWP used in communication with its own NR base station. The LTE base station may use the information regarding the BWP to obtain the numerology used in transmission and reception between the NR base station and the UE. The NR base station may notify the LTE base station in advance of the BWP set by the UE in communication with its own NR and the numerology used in the BWP. The notification may be included, for example, in the signaling that notifies the LTE base station of the RRC setting change of the UE. This can reduce, for example, the amount of signaling between base stations.

[0133] According to the first embodiment, in NR-LTE coexistence, the LTE base station can grasp information regarding the time resources scheduled by the NR base station. As a result, reliability and transmission rate can be ensured in communication between the UE and both base stations.

[0134] Embodiment 2. In the case of BWP switching in the UE, the base station notifies the UE including information on the BWP used for the uplink scheduling grant. The UE uses this information to switch the uplink used BWP and perform uplink transmission. A predetermined time may be provided in the UE, and the BWP used may be switched at the predetermined time. The aforementioned predetermined time may be, for example, the time until the uplink transmission frequency stabilizes in the UE, or may be determined using other methods.

[0135] In the above, the following problem occurs. That is, the base station does not recognize the aforementioned predetermined time in the UE. As a result, a mismatch occurs between the transmission timing of the UE and the reception timing of the base station in communication between the UE and the base station before and after BWP switching, and as a result, a problem occurs in that the reliability and communication rate of the communication decrease.

[0136] A method for solving the foregoing problems is disclosed. The UE notifies the base station of information regarding the BWP switching time of the UE itself. This information may be included in, for example, the UE capabilities. The UE may notify the base station by including this information in the UE capabilities. The base station may use this notification to obtain the BWP switching time in the UE. The base station may perform scheduling for the UE using this BWP switching time. The BWP switching time may be determined, for example, using the time when the RF (Radio Frequency) circuit of the UE itself stabilizes.

[0137] The foregoing BWP switching time may be determined, for example, in microseconds, in a predetermined time unit (e.g., Ts in LTE), or in symbol units. The foregoing BWP switching time may be determined for each numerology. This makes it easier, for example, to perform scheduling in the base station.

[0138] An example thereof will be described with reference to a figure. FIG. 16 is a diagram showing an example in which the UE notifies the base station of BWP switching time information. In the example shown in FIG. 16, the UE notifies the base station by including this information in the UE capabilities.

[0139] When the foregoing method is applied, the following problems occur. That is, the timing at which the UE performs BWP switching is not determined. As a result, for example, when the time resources of the uplink transmission before BWP switching and the uplink transmission after BWP switching are adjacent, a mismatch in the BWP used for transmission and reception occurs between the base station and the UE. As a result, the base station becomes unable to receive the uplink signal before and after BWP switching. This causes a problem that the reliability and communication rate of the uplink communication before and after BWP switching decrease.

[0140] A method for solving the foregoing problems is disclosed. The UE stops the uplink transmission in the slot before BWP switching earlier by an amount equivalent to the BWP switching time. It may also stop the uplink transmission earlier by an amount equal to or more than the BWP switching time, for example, by the time obtained by rounding up the BWP switching time to the symbol unit before BWP switching. The foregoing uplink transmission stop may be performed by signaling (e.g., DCI) from the base station to the UE. For example, the uplink transmission grant after BWP switching may include information regarding the foregoing uplink transmission stop. The signaling may include information regarding the time for which the UE stops the uplink transmission, for example, an amount equivalent to the BWP switching time, or may include information regarding the timing at which the UE stops the uplink transmission, for example, the symbol number at which the uplink transmission is stopped. As another example, the signaling may include information regarding the reason for which the UE stops the uplink transmission, for example, BWP switching. The UE may use the information regarding the reason to stop the foregoing uplink transmission earlier by an amount equivalent to the BWP switching time. The foregoing uplink transmission stop time may be, for example, in symbol units. The foregoing symbol may be, for example, a symbol in the BWP before switching.

[0141] As another example, the foregoing uplink transmission stop may be predefined as a standard regarding the operation of the UE. The UE may assume the uplink scheduling for the BWP switching time. That is, the UE may autonomously stop the uplink transmission for the switching time and perform BWP switching without signaling from the base station. Thereby, for example, the amount of signaling from the base station to the UE can be reduced.

[0142] FIG. 17 is a diagram showing an example of the operation in which the UE stops the uplink transmission in the slot before BWP switching earlier by an amount equivalent to the BWP switching time. In the example shown in FIG. 17, the BWP initially used by the UE, that is, the used BWP at the left end of the figure, is BWP#1.

[0143] In Fig. 17, the base station transmits an uplink grant 1701 to the UE. The uplink grant 1701 includes scheduling information for uplink transmission using slot 1702 in BWP#1. The UE performs uplink transmission in slot 1702 using BWP#1 upon receiving the uplink grant 1701.

[0144] In Fig. 17, the base station transmits an uplink grant 1703 to the UE. The uplink grant 1703 includes scheduling information for uplink transmission using slot 1704 in BWP#2. The UE stops uplink transmission in the time resource 1705 corresponding to the BWP switching time in slot 1702 upon receiving the uplink grant 1703. The UE switches the serving BWP from BWP#1 to BWP#2 and performs uplink transmission in slot 1704.

[0145] The above-described solution may be applied, for example, in preemption. For example, in the above-described solution, uplink transmission using the BWP before switching may be preempted, that is, it may be uplink transmission with a low priority. Uplink transmission using the BWP after switching may preempt, that is, it may be uplink transmission with a high priority. The above-described priority may be determined, for example, by the QCI assigned to the logical channel. This enables, for example, ensuring the reliability in preemption.

[0146] Fig. 18 is a diagram showing an example of an operation in which the UE stops uplink transmission in a slot before BWP switching earlier by an amount corresponding to the BWP switching time in preemption communication. In the example shown in Fig. 18, in the uplink slot before BWP switching, the base station transmits a preemption message to the UE. After the UE interrupts the transmission of the uplink slot targeted for preemption and performs BWP switching, it performs uplink transmission using the BWP newly assigned by the preemption message. In Fig. 18, elements common to Fig. 17 are assigned the same reference numerals, and common descriptions are omitted.

[0147] The uplink grant 1701 and slot 1702 shown in FIG. 18 are the same as those in FIG. 17.

[0148] In FIG. 18, the base station notifies the UE of a preemption grant 1803. The preemption grant 1803 includes scheduling information for uplink preemption transmission using slot 1804 in BWP#2. The preemption grant 1803 may include a preemption indication (PI) for the uplink transmission of slot 1702. The UE may stop the uplink transmission using BWP#1 at time resource 1805 using the preemption grant 1803. The time resource 1805 may include a time resource that is retrograded by the BWP switching time from slot 1804. The UE switches the serving BWP from BWP#1 to BWP#2 using the preemption grant 1803 and performs uplink preemption transmission in slot 1704.

[0149] The above-described solution may be applied when the numerology before and after the switching is the same. By this, the same effect as described above can be obtained.

[0150] FIG. 19 is a diagram showing an example of terminating the transmission of the uplink slot before BWP switching earlier by the amount of the BWP switching time when the numerology before and after BWP switching is the same. In FIG. 19, the same reference numerals are assigned to the elements common to FIG. 17, and the common description is omitted.

[0151] The uplink grant 1701 and slot 1702 shown in FIG. 19 are the same as those in FIG. 17.

[0152] In FIG. 19, the base station transmits an uplink grant 1903 to the UE. The uplink grant 1903 includes scheduling information for uplink transmission using slot 1904 in BWP#2. Upon receiving the uplink grant 1903, the UE stops uplink transmission in time resource 1705 corresponding to the BWP switching time in slot 1702. The UE switches the serving BWP from BWP#1 to BWP#2 and performs uplink transmission in slot 1904.

[0153] In this solution, the BWP switching time may be a timing before the scheduling start timing after BWP switching, or may be a timing before the scheduling end timing before BWP switching. For example, when the scheduling after BWP switching starts from a symbol in the middle of a slot, the BWP switching time may be provided before the symbol. This enables the application of the above solution to BWP switching in, for example, non-slot scheduling. The above non-slot scheduling may be, for example, non-slot scheduling in preemption. This ensures reliability, for example, even in preemption using non-slot scheduling.

[0154] Other solutions are disclosed. The UE may stop the uplink transmission in the slot after the BWP switching until a time equivalent to the BWP switching time. The UE may also stop the uplink transmission until a time longer than the time equivalent to the BWP switching time, for example, until a time obtained by rounding up the BWP switching time to the symbol unit before the BWP switching. The above-mentioned uplink transmission stop may be performed by signaling (e.g., DCI) from the base station to the UE. For example, the above-mentioned information regarding the uplink transmission stop may be included in the uplink transmission grant after the BWP switching. The signaling may include information regarding the time for which the UE stops the uplink transmission, for example, the time equivalent to the BWP switching time, or may include information regarding the timing at which the UE stops the uplink transmission, for example, the symbol number at which the uplink transmission is stopped. As another example, the signaling may include information regarding the reason for which the UE stops the uplink transmission, for example, BWP switching. The UE may use the information regarding the reason to start the above-mentioned uplink transmission late by a time equivalent to the BWP switching time. The above-mentioned uplink transmission stop time may be, for example, in symbol units. The above-mentioned symbol may be, for example, a symbol in the BWP after the switching.

[0155] As another example, the above-mentioned uplink transmission stop may be predefined as a standard regarding the operation of the UE. The UE may assume the empty scheduling for the switching time. That is, the UE may autonomously perform the BWP switching at the switching time and start the uplink transmission without signaling from the base station. This can reduce, for example, the amount of signaling from the base station to the UE.

[0156] In the above, the numerology before and after the BWP switching may be the same or different. The same effects as described above can be obtained.

[0157] FIG. 20 is a diagram showing an example in which the transmission of the uplink slot after the BWP switching is started late by a time equivalent to the BWP switching time. FIG. 20 shows the case where the numerology before and after the BWP switching is the same. In FIG. 20, elements common to FIG. 17 are given the same reference numerals, and the common descriptions are omitted.

[0158] The uplink grant 1701 and slot 1702 shown in FIG. 20 are the same as those in FIG. 17.

[0159] In FIG. 20, the base station transmits an uplink grant 1903 to the UE. The uplink grant 1903 includes scheduling information for uplink transmission using slot 1904 in BWP#2. The UE switches the serving BWP from BWP#1 to BWP#2 after the uplink transmission in slot 1702 upon receiving the uplink grant 1903. The UE performs uplink transmission in slot 1904 after the elapse of the time resource 1705 corresponding to the BWP switching time.

[0160] FIG. 20 shows the case where the numerology is the same before and after BWP switching, but the numerology may be different before and after BWP switching. The same effect as described above can be obtained.

[0161] In the above, the BWP switching time may be at a timing after the scheduling start timing after BWP switching, or at a timing after the scheduling end timing before BWP switching. For example, when the scheduling after BWP switching starts from a symbol in the middle of a slot, the BWP switching time may be provided after that symbol. As a result, for example, the above-described solution can also be applied to BWP switching in non-slot scheduling.

[0162] Other solutions are disclosed. The BWP switching time may be distributed between the slot before the BWP switch and the slot after the BWP switch. The above distribution may be, for example, equal in the slots before and after the BWP switch. As another example, the above distribution may be different in the slots before and after the BWP switch. For example, the above distribution may be determined using the slot length. As an example where the distribution is determined by the slot length, when the slot lengths before and after the BWP switch are 4:1, the distribution of the BWP switching time before and after the BWP switch may be 4:1. Thus, for example, it is possible to make the ratio of the uplink transmission stop time in the scheduled time resources the same before and after the BWP switch. As a result, the base station can ensure the reliability in decoding the uplink data both before and after the BWP using error correction or the like. As another example, the amount of data to be aborted may be made equal. In the above, the allocated uplink transmission stop time may be given in units of the symbol length before and after the BWP switch respectively, or may be rounded up in units of the symbol length before and after the BWP switch respectively.

[0163] The base station may determine the above distribution. The base station may notify the UE of information regarding the above distribution. For the notification, for example, RRC signaling may be used, MAC signaling may be used, or DCI may be used. The UE may stop the uplink transmission at the above allocated BWP switching time. The above uplink transmission stop may be performed by signaling from the base station to the UE (for example, DCI). For example, information regarding the above uplink transmission stop may be included in the uplink transmission grant after the BWP switch. The base station may give the uplink transmission stop time before and after the BWP switch respectively as the time in units of symbols before and after the BWP switch respectively.

[0164] As another example, the above-mentioned allocation may be predetermined as a standard. The above-mentioned allocation may be, for example, equal before and after BWP switching, may be determined using the slot length, or may be determined using other information. The UE may assume the uplink scheduling before and after the BWP switching time using the allocation. That is, the UE may autonomously perform BWP switching at the switching time without signaling from the base station and start uplink transmission. This can reduce, for example, the amount of signaling from the base station to the UE.

[0165] FIG. 21 is a diagram showing an example of allocating a transmission suspension time corresponding to the BWP switching time at the rear end of the uplink slot before BWP switching and the front end of the uplink slot after BWP switching. FIG. 21 shows an example in which the allocation of the BWP switching time before and after BWP switching is equal. In FIG. 21, elements common to FIG. 17 are given the same reference numerals, and the common description is omitted.

[0166] The uplink grant 1701 and slot 1702 shown in FIG. 21 are the same as those in FIG. 17.

[0167] In FIG. 21, the base station transmits an uplink grant 1903 to the UE. The uplink grant 1903 includes scheduling information for uplink transmission using the slot 1904 in BWP#2. The UE stops uplink transmission in the time resource 2105 corresponding to the time allocated to the slot before BWP switching in the BWP switching time in the slot 1702 upon receiving the uplink grant 1903. The UE switches the used BWP from BWP#1 to BWP#2. The UE performs uplink transmission after the elapse of the time resource 2106 corresponding to the time allocated to the slot after BWP switching in the BWP switching time in the slot 1904.

[0168] FIG. 21 shows the case where the time resources 2105 and 2106 are equal, but the time resources 2105 and 2106 may be different. Also, FIG. 21 shows the case where the numerology is the same before and after the BWP switching, but the numerology may be different before and after the BWP switching. The same effects as described above can be obtained.

[0169] In the above, the BWP switching time may be distributed before and after the scheduling start timing after the BWP switching, or may be distributed before and after the scheduling end timing before the BWP switching. For example, when the scheduling after the BWP switching starts from a symbol in the middle of a slot, the BWP switching time may be provided after the symbol. Thus, for example, the above-described solution can also be applied to the BWP switching in non-slot scheduling.

[0170] Another solution is disclosed. The BWP switching time in the UE may be determined in advance by a standard. The UE may perform the BWP switching within the time determined by the standard. The base station may perform scheduling for the UE using the time determined by the standard. The BWP switching time may be determined by, for example, the frequency band before the switching, the frequency band after the switching, or the combination of the frequency bands before and after the switching. Thus, for example, since it is not necessary to notify information regarding the BWP switching time from the UE to the base station, the signaling amount between the UE and the base station can be reduced.

[0171] Regarding which solution in the second embodiment is to be used, it may be determined in advance by a standard, or the base station may determine it and notify the UE. For example, in preemption communication, the BWP switching time may be allocated within the time resource scheduled for the uplink transmission to be preempted, or in other cases, the BWP switching time may be allocated within the time resource scheduled after the BWP switching. This enables ensuring the reliability in communication that requires high reliability such as URLLC.

[0172] In the second embodiment, the uplink transmission stop of the UE may be implemented by not transmitting the data mapped to the symbols of the stop period, or may be implemented by remapping (i.e., re-encoding and modulating) to the symbols excluding the period. A combination of both may also be possible. For example, the uplink transmission stop before the BWP switching may be implemented by not transmitting the data mapped to the symbols of the stop period. For example, the uplink transmission stop after the BWP switching may be implemented by remapping to the symbols excluding the period. This enables suppressing an increase in the processing amount at the UE while ensuring the reliability of the uplink transmission at the UE.

[0173] The method disclosed in the second embodiment may be applied in SUL / non-SUL switching. In the above application, the BWP switching in the second embodiment may be read as SUL / non-SUL switching and applied. As another example, in both BWP switching and SUL / non-SUL switching, the method disclosed in the second embodiment may be used. The BWP switching time and the SUL / non-SUL switching time may be common or different. For example, making the BWP switching time and the SUL / non-SUL switching time common enables reducing the size of the UE capability.

[0174] According to the second embodiment, it is possible to prevent unnecessary transmission and reception at the time of BWP switching. As a result, there is an effect that it is possible to prevent a decrease in the reliability and transmission rate of communication.

[0175] Each of the above-described embodiments and their modifications are merely examples of the present invention, and within the scope of the present invention, the embodiments and their modifications can be freely combined. Also, any component of each embodiment and its modification can be appropriately changed or omitted.

[0176] For example, in each of the above-described embodiments and their modifications, a slot is an example of a time unit of communication in a fifth-generation base station communication system. It may also be a scheduling unit. In each of the above-described embodiments and their modifications, the processing described as being in slot units may be performed in TTI units, subframe units, sub-slot units, or mini-slot units.

[0177] Although the present invention has been described in detail, the above description is illustrative in all aspects and the present invention is not limited thereto. Innumerable modifications that are not illustrated can be assumed without departing from the scope of the present invention.

Description of Reference Numerals

[0178] 200 Communication system, 202 Communication terminal device, 203 Base station device.

Claims

1. A communication terminal configured to be capable of wirelessly communicating with a base station, The communication terminal notifies the base station of information related to a switching time of a BWP (Bandwidth Part); The switching time is determined for each numerology. Communications terminal.

2. The base station performs scheduling for the communication terminal based on the information regarding the switching time. The communication terminal according to claim 1.

3. the communication terminal autonomously stops uplink transmission of the BWP for the switching time, and switches the BWP used for communication with the base station during the switching time. The communication terminal according to claim 1.

4. A base station configured to be capable of wirelessly communicating with a communication terminal, Receive information regarding a switching time of a BWP (Bandwidth Part) from the communication terminal, the switching time being determined for each numerology; performing scheduling for the communication terminal based on the information regarding the switching time; Base station.

5. A base station; a communication terminal configured to be capable of wireless communication with the base station; Equipped with The communication terminal notifies the base station of information related to a switching time of a BWP (Bandwidth Part); The switching time is determined for each numerology. Communication systems.

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