Communication system, base station, and user equipment

Abstract

To provide a technology that can shorten a time for beam switching processing.SOLUTION: A communication system includes a user device, and a base station that communicates with the user device by switching between multiple beams that can be formed by beamforming. The user device performs synchronization processing on the basis of a signal transmitted using the beam.SELECTED DRAWING: Figure 27

Description

Technical Field

[0001] The present invention relates to a communication system and the like.

Background Art

[0002] In 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 10). 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 2 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 at 40 ms intervals. There is no explicit signaling at 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 regarding 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 a CQI (Channel Quality Indicator) report. The CQI is quality information indicating the quality of received data or the communication channel quality. The PUCCH also carries a 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 channel for downlink transmission from a base station to a communication terminal. The PHICH carries the Ack / Nack, which is a response signal for uplink transmission. The Physical Random Access Channel (PRACH) is a channel for uplink transmission from a communication terminal to a base station. The PRACH carries a random access preamble.

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

[0015] The transport channel described in Non-Patent Document 1 (Chapter 5) will be explained. Among the downlink transport channels, the broadcast channel (Broadcast Channel: BCH) is notified to the entire coverage of the base station (cell). The BCH is mapped to the physical broadcast channel (PBCH).

[0016] For the downlink shared channel (DL-SCH), retransmission control by HARQ (Hybrid ARQ) is applied. The DL-SCH can notify the entire 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 communication terminals for power consumption reduction of the communication terminals. The DL-SCH is mapped to the physical downlink shared channel (PDSCH).

[0017] The paging channel (PCH) supports DRX of communication terminals to enable low power consumption of communication terminals. The PCH requires notification to the entire 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.

[0018] The multicast channel (MCH) is used for notification to the entire coverage area of the base station (cell). The MCH supports SFN synthesis of MBMS (Multimedia Broadcast Multicast Service) services (MTCH and MCCH) in multi-cell transmission. The MCH supports semi-static resource allocation. The MCH is mapped to the PMCH.

[0019] Among the uplink transport channels, for the uplink shared channel (UL-SCH), retransmission control by HARQ (Hybrid ARQ) is applied. The UL-SCH supports dynamic or semi-static resource allocation. The UL-SCH is mapped to the physical uplink shared channel (PUSCH).

[0020] The Random Access Channel (RACH) is limited to control information. The RACH has a risk of collision. The RACH is mapped to the Physical Random Access Channel (PRACH).

[0021] Hybrid Automatic Repeat reQuest (HARQ) will be described. 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 at the time of retransmission.

[0022] An example of the retransmission method will be described. When the receiving side cannot correctly decode the received data, in other words, when a Cyclic Redundancy Check (CRC) error occurs (CRC = NG), the receiving side transmits a "Nack" to the transmitting side. The transmitting side that receives the "Nack" retransmits the data. When the receiving side can correctly decode the received data, in other words, when no CRC error occurs (CRC = OK), the receiving side transmits an "Ack" to the transmitting side. The transmitting side that receives the "Ack" transmits the next data.

[0023] The 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).

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The Dedicated Control Channel (DCCH) is a channel for transmitting dedicated control information between a communication terminal and the network on a one-to-one basis. The DCCH is used when the communication terminal has an RRC connection. In the uplink, the DCCH is mapped to the Uplink Shared Channel (UL-SCH), and in the downlink, it is mapped to the Downlink Shared Channel (DL-SCH).

[0028] The Dedicated Traffic Channel (DTCH) is a one-to-one communication channel to an individual communication terminal for the transmission of user information. The DTCH exists for both the uplink and the downlink. The DTCH is mapped to the Uplink Shared Channel (UL-SCH) in the uplink and to the Downlink Shared Channel (DL-SCH) in the downlink.

[0029] 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).

[0030] CGI stands for Cell Global Identifier. ECGI stands for E-UTRAN Cell Global Identifier. In LTE, Long Term Evolution Advanced (LTE-A) which will be described later, and Universal Mobile Telecommunication System (UMTS), Closed Subscriber Group (CSG) cells are introduced.

[0031] A Closed Subscriber Group (CSG) cell is a cell in which the operator has identified the available subscribers (hereinafter sometimes referred to as "cells for specific subscribers"). The identified subscribers are permitted to access one or more cells of a Public Land Mobile Network (PLMN). One or more cells to which the identified subscribers are permitted access are called "CSG cells". However, there are access restrictions to the PLMN.

[0032] A CSG cell is part of a PLMN that announces a unique CSG identity (CSG ID; CSG-ID) and announces "TRUE" in the CSG Indication. Members of a pre-registered and permitted subscriber group access the CSG cell using the CSG-ID, which is access permission information.

[0033] The CSG-ID is announced by a CSG cell or a cell. There are multiple CSG-IDs in an LTE communication system. The CSG-ID is used by a communication terminal (UE) to facilitate access by CSG-related members.

[0034] Location tracking of a communication terminal is performed in units of an area consisting of one or more cells. Location tracking is performed to track the location of the communication terminal even in the standby state and to enable calling the communication terminal, in other words, to enable the communication terminal to be paged. The area for this location tracking of the communication terminal is called a tracking area.

[0035] In 3GPP, base stations called Home-NodeB (Home-NB; HNB) and Home-eNodeB (Home-eNB; HeNB) are being considered. The HNB in UTRAN and the HeNB in E-UTRAN are base stations for access services for, for example, homes, corporations, and commercial use. Non-Patent Document 2 discloses three different modes of access to HeNB and HNB. Specifically, an open access mode, a closed access mode, and a hybrid access mode are disclosed.

[0036] In addition, 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.

[0037] In the LTE-A system, in order to support a wider frequency bandwidth (transmission bandwidths) up to 100 MHz, carrier aggregation (CA) is being studied, in which two or more component carriers (CC) are aggregated (also referred to as "aggregation"). CA is described in Non-Patent Document 1.

[0038] 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).

[0039] According to the capabilities of the UE, a Secondary Cell (SCell) is configured to form a set with the PCell and the serving cell. 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).

[0040] For one UE, a set consisting of one PCell and a serving cell composed of one or more SCells is configured.

[0041] In addition, as new technologies in LTE-A, there are technologies such as Wider bandwidth extension and Coordinated Multiple Point transmission and reception (CoMP) technology. Regarding CoMP being considered for LTE-A by 3GPP, it is described in Non-Patent Document 1.

[0042] The traffic volume of the mobile network is on an increasing trend, and the communication speed is also accelerating. When LTE and LTE-A are fully operational, it is expected that the communication speed will be further increased.

[0043] In addition, in 3GPP, in order to cope with future huge traffic, it has been considered 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 have been considered. Specifically, there is Dual Connectivity (abbreviation: DC) in which a UE connects to two eNBs to perform communication. DC is described in Non-Patent Document 1.

[0044] Among the eNBs that perform Dual Connectivity (DC), one may be referred to as the "Master eNB (abbreviation: MeNB)", and the other may be referred to as the "Secondary eNB (abbreviation: SeNB)".

[0045] Furthermore, for advanced mobile communications, a fifth-generation (hereinafter sometimes referred to as "5G") radio access system aiming to start services after 2020 has been considered. For example, in Europe, the requirements for 5G have been summarized by a group called METIS (see Non-Patent Document 5).

[0046] 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 reduction of devices are listed as requirements.

[0047] In order to meet such requirements, using a wide bandwidth for frequency to increase the data transmission capacity and increasing the frequency utilization efficiency to increase the data transmission speed have been considered. To achieve these, technologies such as MIMO (Multiple Input Multiple Output) using multi-element antennas and beamforming that enable spatial multiplexing have been considered.

Prior Art Documents

Non-Patent Documents

[0048]

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

Summary of the Invention

Problems to be Solved by the Invention

[0049] In DC, split bearers are supported. In split bearers, SPS (Semi-Persistent Scheduling) is supported not only for MeNB but also for SeNB (see Non-Patent Document 6).

[0050] In 3GPP, a method of transmitting a Buffer Status Report (BSR) when an uplink split bearer is being executed has been proposed to be a method based on Double Reporting And Threshold (DRAT) (see Non-Patent Document 7). When DRAT is executed for an uplink split bearer, the UE transmits data to one predetermined eNB when the amount of uplink data is equal to or less than the DRAT threshold, and does not transmit data to the other eNB.

[0051] However, there is no regulation regarding the operation of SPS when the amount of uplink data becomes equal to or less than the DRAT threshold, such as whether padding transmission by the UE is possible, and there has been no discussion on this matter either.

[0052] Without a regulation on the operation of SPS, the implicit release function by padding transmission does not work properly. As a result, unstable operations occur between the eNB and the UE. Consequently, there is a possibility of causing malfunction.

[0053] An object of the present invention is to provide a technology capable of reducing deterioration of communication quality and disconnection of communication.

Means for Solving the Problems

[0054] A communication system according to the present invention is a communication system including a user device and a base station that communicates with the user device while switching between a plurality of beams that can be formed by beamforming, wherein the user device executes synchronization processing based on a signal transmitted using a beam. A base station according to the present invention is a base station in a communication system including a user device and a base station that communicates with the user device while switching between a plurality of beams that can be formed by beamforming, and transmits a signal that is transmitted using a beam and is used for synchronization processing in the user device. The user equipment according to the present invention is a user equipment in a communication system including a user equipment and a base station that communicates with the user equipment while switching between a plurality of beams that can be formed by beamforming, and performs synchronization processing based on a signal transmitted using a beam.

Effects of the Invention

[0055] According to the present invention, it is possible to shorten the time for beam switching processing.

[0056] The object, features, aspects, and advantages of the present invention will become clearer from the following detailed description and the accompanying drawings.

Brief Description of the Drawings

[0057]

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Mode for Carrying Out the Invention

[0058] Embodiment 1. Figure 2 is a block diagram showing the overall configuration of a communication system 200 of the LTE system being discussed in 3GPP. An explanation of Figure 2 will be given. 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.

[0059] 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".

[0060] If a control protocol for the mobile terminal 202, such as RRC (Radio Resource Control), and user planes, such as PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), and PHY (Physical layer), terminate at the base station 203, then the E-UTRAN is composed of one or more base stations 203.

[0061] The control protocol RRC (Radio Resource Control) between the mobile terminal 202 and the base station 203 performs functions such as broadcast, paging, and RRC connection management. As the states of the base station 203 and the mobile terminal 202 in RRC, there are RRC_IDLE and RRC_CONNECTED.

[0062] In the RRC_IDLE state, PLMN (Public Land Mobile Network) selection, system information (SI) notification, paging, cell re-selection, mobility, etc. are performed. In the RRC_CONNECTED state, the mobile terminal has an RRC connection and can transmit and receive data with the network. Also in the RRC_CONNECTED state, handover (HO), measurement of neighbour cells, etc. are performed.

[0063] The base station 203 is classified into an eNB 207 and a Home-eNB 206. The communication system 200 includes an eNB group 203-1 including a plurality of eNBs 207 and a Home-eNB group 203-2 including a plurality of Home-eNBs 206. Also, a system composed of an EPC (Evolved Packet Core) which is a core network and an E-UTRAN 201 which is a radio access network is called an EPS (Evolved Packet System). Sometimes, the combination of the core network EPC and the radio access network E-UTRAN 201 is referred to as the "network".

[0064] The eNB 207 is connected to a mobility management entity (MME), or a serving gateway (S-GW), or an MME / S-GW unit (hereinafter sometimes referred to as the "MME unit") 204 including an MME and an S-GW through an 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 to each other through an X2 interface, and control information is communicated between the eNBs 207.

[0065] Home-eNB 206 is connected to the MME unit 204 via the S1 interface, and control information is communicated between the Home-eNB 206 and the MME unit 204. A plurality of Home-eNBs 206 are connected to one MME unit 204. Alternatively, the Home-eNB 206 is connected to the MME unit 204 via the HeNBGW (Home-eNB GateWay) 205. The Home-eNB 206 and the HeNBGW 205 are connected by the S1 interface, and the HeNBGW 205 and the MME unit 204 are connected via the S1 interface.

[0066] One or more Home-eNBs 206 are connected to one HeNBGW 205, and information is communicated through the S1 interface. The HeNBGW 205 is connected to one or more MME units 204, and information is communicated through the S1 interface.

[0067] The MME unit 204 and the HeNBGW 205 are upper-level devices, specifically upper-level nodes, and control the connection between the base stations eNB 207 and Home-eNB 206 and the mobile terminal (UE) 202. The MME unit 204 constitutes the EPC which is the core network. The base stations 203 and the HeNBGW 205 constitute the E-UTRAN 201.

[0068] Furthermore, in 3GPP, the following configurations are being considered. The X2 interface between Home-eNBs 206 is supported. That is, the Home-eNBs 206 are connected by the X2 interface, and control information is communicated between the Home-eNBs 206. From the MME unit 204, the HeNBGW 205 appears as a Home-eNB 206. From the Home-eNB 206, the HeNBGW 205 appears as the MME unit 204.

[0069] In both the case where the Home-eNB 206 is connected to the MME unit 204 via the HeNBGW 205 and the case where it is directly connected to the MME unit 204, the interface between the Home-eNB 206 and the MME unit 204 is the same S1 interface.

[0070] The base station 203 may constitute one cell or a plurality of cells. Each cell has a range predetermined as coverage within which it can communicate with the mobile terminal 202, and performs wireless communication with the mobile terminal 202 within the coverage. When one base station 203 constitutes a plurality of cells, each individual cell is configured to be able to communicate with the mobile terminal 202.

[0071] FIG. 3 is a block diagram showing the configuration of the mobile terminal 202 shown in FIG. 2, which is a communication terminal according to the present invention. The transmission process of the mobile terminal 202 shown in FIG. 3 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 subjected to encoding processing such as error correction. There may be data that is directly output from the transmission data buffer unit 303 to the modulation unit 305 without being subjected to the encoding process. The data encoded by the encoder unit 304 is subjected to modulation processing 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 wireless transmission frequency. Thereafter, a transmission signal is transmitted from the antenna 307 to the base station 203.

[0072] Also, the reception process of the mobile terminal 202 is executed as follows. A wireless signal from the base station 203 is received by the antenna 307. The received signal is converted from the wireless reception frequency to a baseband signal by the frequency conversion unit 306, and demodulation processing is performed by the demodulation unit 308. The demodulated data is passed to the decoder unit 309, where 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. 3, the control unit 310 is connected to each of the units 301 to 309.

[0073] FIG. 4 is a block diagram showing the configuration of the base station 203 shown in FIG. 2, which is a base station according to the present invention. The transmission process of the base station 203 shown in FIG. 4 will be described. The EPC communication unit 401 transmits and receives data between the base station 203 and the EPC (such as the MME unit 204), the HeNBGW 205, etc. The other base station communication unit 402 transmits and receives data with other base stations. The EPC communication unit 401 and the other base station communication unit 402 respectively 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 and the other base station communication unit 402, are stored in the transmission data buffer unit 404.

[0074] The data stored in the transmission data buffer unit 404 is passed to the encoder unit 405, and encoding processing such as error correction is performed. There may be data that is directly output from the transmission data buffer unit 404 to the modulation unit 406 without undergoing encoding processing. The encoded data is subjected to modulation processing 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 radio transmission frequency. Thereafter, a transmission signal is transmitted from the antenna 408 to one or more mobile terminals 202.

[0075] Also, the reception process of the base station 203 is executed as follows. A radio signal from one or more mobile terminals 202 is received by the antenna 408. The received signal is converted from the radio reception frequency to a baseband signal by the frequency conversion unit 407, and demodulation processing is performed by the demodulation unit 409. The demodulated data is passed to the decoder unit 410, and decoding processing such as error correction is 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 are controlled by the control unit 411. Therefore, although omitted in FIG. 4, the control unit 411 is connected to each unit 401 - 410.

[0076] FIG. 5 is a block diagram showing the configuration of the MME according to the present invention. In FIG. 5, 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.

[0077] 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.

[0078] The HeNB GW communication unit 504 is provided when the HeNB GW 205 exists and transmits and receives data via the interface (IF) between the MME 204a and the HeNB GW 205 depending on the type of information. The control data received from the HeNB GW communication unit 504 is passed from the HeNB GW 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 HeNB GWs 205 via the HeNB GW communication unit 504.

[0079] 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 overall processing for the control plane. The NAS security unit 505-1 performs security for NAS (Non-Access Stratum) messages. The SAE bearer control unit 505-2 performs management of SAE (System Architecture Evolution) bearers. 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.

[0080] 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, CSG-ID, and white list of the Home-eNB 206 connected to the MME 204a may be performed by the idle state mobility management unit 505-3.

[0081] Next, an example of a cell search method in a communication system is shown. FIG. 6 is a flowchart showing an overview from cell search to standby operation performed by a communication terminal (UE) in an LTE-based 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.

[0082] The combination of P-SS and S-SS is called the synchronization signal (SS). A synchronization code corresponding one-to-one to the PCI assigned to each cell is assigned to the synchronization signal (SS). 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).

[0083] 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 (reference signal received power: RSRP) of the RS is measured. A code corresponding one-to-one to the PCI is used for the reference signal (RS). By correlating with that code, separation from other cells is possible. 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.

[0084] 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.

[0085] 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, for example, the DL (downlink) system bandwidth (also called transmission bandwidth configuration: dl - bandwidth), the number of transmission antennas, the SFN (System Frame Number), etc.

[0086] Next, in step ST605, based on the cell configuration information of 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 of other SIBs (SIBk; k is an integer greater than or equal to 2). Also, the SIB1 contains the Tracking Area Code (TAC).

[0087] 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 already held by the communication terminal. 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.

[0088] 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 of 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.

[0089] 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.

[0090] Due to the spread of smartphones and tablet terminal devices, traffic by cellular wireless communication has increased explosively, and a shortage of wireless resources is a concern worldwide. In response, in order to improve the frequency utilization efficiency, it is being considered to reduce the cell size and promote spatial separation.

[0091] In the configuration of a conventional cell, a cell constituted 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 constituted by a plurality of eNBs.

[0092] When the cell size is reduced, a cell constituted by an eNB has a coverage area that is narrower than that of a cell constituted by a conventional eNB. Therefore, in order to cover a certain area as in the conventional case, a larger number of small-sized eNBs are required compared to conventional eNBs.

[0093] In the following description, a cell with a relatively large coverage, such as a cell configured by a conventional eNB, is referred to as a "macro cell", and the eNB constituting the macro cell is referred to as a "macro eNB". Also, a cell with a relatively small coverage, such as a small cell, is referred to as a "small cell", and the eNB constituting the small cell is referred to as a "small eNB".

[0094] The macro eNB may be, for example, a "Wide Area Base Station" described in Non-Patent Document 7.

[0095] 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 constituting a pico cell, a femto eNB constituting 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). Also, the small eNB may be a "Local Area Base Station" or a "Home Base Station" described in Non-Patent Document 7.

[0096] FIG. 7 is a diagram showing the concept of the cell configuration when a macro eNB and a small eNB coexist. The macro cell configured by the macro eNB has a relatively wide coverage area 701. The small cell configured by the small eNB has a coverage area 702 that is smaller in range compared to the coverage area 701 of the macro eNB (macro cell).

[0097] When multiple eNBs coexist, the coverage of a cell formed by a certain eNB may be included within the coverage of a cell formed by another eNB. In the cell configuration shown in FIG. 7, as indicated by reference numeral "704" or "705", the coverage 702 of a small cell formed by a small eNB may be included within the coverage 701 of a macro cell formed by a macro eNB.

[0098] Also, as indicated by reference numeral "705", there may be a case where the coverages 702 of multiple, for example, two small cells are included within the coverage 701 of one macro cell. The mobile terminal (UE) 703 is included within the coverage 702 of a small cell, for example, and communicates via the small cell.

[0099] Also, in the cell configuration shown in FIG. 7, as indicated by reference numeral "706", a complex overlap may occur between the coverage 701 of a macro cell formed by a macro eNB and the coverage 702 of a small cell formed by a small eNB.

[0100] Also, as indicated by reference numeral "707", there may be a case where the coverage 701 of a macro cell formed by a macro eNB and the coverage 702 of a small cell formed by a small eNB do not overlap.

[0101] Furthermore, as indicated by reference numeral "708", there may be a case where the coverages 702 of a number of small cells formed by a number of small eNBs are configured within the coverage 701 of one macro cell formed by one macro eNB.

[0102] In dual connectivity (DC), split bearers are supported. A split bearer refers to a bearer that is split (split) into a direct path between the MeNB and the UE and a path between the MeNB and the UE via the SeNB.

[0103] In a split bearer, SPS (Semi-Persistent Scheduling) is supported not only for the MeNB but also for the SeNB (see Non-Patent Document 6). SPS can be set simultaneously and independently for the MeNB and the SeNB.

[0104] SPS is a scheduling method that enables the eNB to quasi-statically allocate radio resources to the UE over a long period of multiple subframes. This allows the eNB to avoid having to transmit DL allocation information or UL grant information on individual control channels such as the PDCCH and EPDCCH to the UE in each subframe.

[0105] Regarding SPS in 3GPP, it is described in Non-Patent Document 9.

[0106] In RRC individual signaling, settings such as the SPS interval, the C-RNTI (Cell Radio Network Temporary Identifier) for SPS, and the number of empty transmissions before implicit release in the UL (hereinafter sometimes referred to as the "number of empty transmissions before release") are notified to the UE. This enables SPS to be executed. As the number of empty transmissions before release, the parameter "implicitReleaseAfter" is used. In the following description, the number of empty transmissions before release may be represented by the symbol "n".

[0107] Also, SPS is disabled by RRC individual signaling. As a result, the corresponding DL allocation information or UL grant information is discarded. The C-RNTI for SPS may be referred to as the SPS C-RNTI.

[0108] SPS is activated (started) and deactivated (ended) by the PDCCH or EPDCCH. The SPS C-RNTI is masked on the CRC of this PDCCH or EPDCCH.

[0109] In particular, for the uplink SPS, a method for terminating the execution of SPS called implicit release has been determined. When there is no uplink transmission data, the UE transmits a MAC PDU (Protocol Data Unit) including at least one of a padding bit and a padding BSR. This transmission may be referred to as a dummy transmission or a padding transmission. When this transmission is continuously performed for the number of times set as the number of dummy transmissions before the aforementioned UL implicit release, the uplink grant information is immediately cleared.

[0110] As a result, also in the eNB, when receiving the transmission from the UE continuously for the number of times set as the number of dummy transmissions before the UL implicit release, the uplink SPS setting is invalidated. By invalidating the SPS setting, the eNB can use the radio resources allocated by the SPS setting for other UEs.

[0111] FIG. 8 is a diagram for explaining an operation example of the uplink SPS.

[0112] In step ST801, the eNB notifies the UE of the configuration of the SPS resource and the SPS C-RNTI used when receiving the PDCCH by RRC individual signaling.

[0113] The UE that has received the configuration of the SPS resource and the SPS C-RNTI in step ST801 detects the PDCCH using the SPS C-RNTI.

[0114] In step ST802, the eNB notifies the UE of an instruction to start (activate) the execution of SPS. When the UE that has received the instruction to start the execution of SPS in step ST802 detects the first scheduling, the SPS is activated. That is, the execution of SPS is started. And the scheduling continues until it is deactivated, that is, until the execution of SPS is terminated.

[0115] In step ST803 and step ST804, SPS is executed with the scheduled SPS resource between the eNB and the UE. In step ST803 and step ST804, the UE transmits uplink data to the eNB using the configured SPS resource.

[0116] In step ST805, when there is no transmission data left in the configured SPS resource, the UE performs padding transmission.

[0117] In step ST805 and step ST806, when the UE continuously performs padding transmission for the number of times set as the number of empty transmissions before release, in step ST807, the UE clears the SPS. Here, the number of empty transmissions before release is set to 2.

[0118] In step ST805 and step ST806, when the eNB also continuously receives padding transmission from the UE for the number of times set as the number of empty transmissions before release, in step ST807, the eNB releases the uplink SPS configuration.

[0119] As described above, split bearers are supported in DC. In 3GPP, it has been proposed to use the Double Reporting And Threshold (DRAT) method for the transmission method of the Buffer Status Report (BSR) when performing uplink split bearers (see Non-Patent Document 7).

[0120] Figures 9 and 10 are diagrams for explaining the DRAT-based transmission method. Figure 9 shows the case where the amount of uplink PDCP data is less than a predetermined threshold (Th). Figure 10 shows the case where the amount of uplink PDCP data is greater than a predetermined threshold (Th).

[0121] In FIG. 9, UE 905 includes Medium Access Control (MAC) 907, Radio Link Control (RLC) 908, MAC 909, RLC 910, and Packet Data Convergence Protocol (PDCP) 911. MAC 907 is used for MeNB 901. RLC 908 is used for MeNB 901. MAC 909 is used for SeNB 902. RLC 910 is used for SeNB 902.

[0122] In FIG. 10, UE 906 includes MAC 912, RLC 913, MAC 914, RLC 915, and PDCP 916. MAC 912 is used for MeNB 903. RLC 913 is used for MeNB 903. MAC 914 is used for SeNB 904. RLC 915 is used for SeNB 904.

[0123] In DRAT, as shown in FIG. 9, when the data volume of PDCP 911 is less than or equal to a predetermined threshold, the buffer status (abbreviated as BS) is reported to one eNB, that is, MeNB 901 or SeNB 902. Which eNB of MeNB 901 and SeNB 902 to report the BS to is set by RRC signaling. The one eNB set as the eNB to report the BS is referred to as the "1st-eNB". FIG. 9 shows the case of reporting the BS to MeNB 901.

[0124] As shown in FIG. 10, when the data volume of PDCP 916 is greater than a predetermined threshold, the BS of the same data volume of PDCP 916 is reported to both eNBs, that is, the 1st-eNB and the 2nd-eNB. In FIG. 10, the 1st-eNB is MeNB 903 and the 2nd-eNB is SeNB 904. The predetermined threshold is set for each radio bearer (RB).

[0125] FIG. 9 may be the case where the amount of data of the uplink PDCP is smaller than a predetermined threshold (Th), and FIG. 10 may be the case where the amount of data of the uplink PDCP is equal to or greater than the predetermined threshold (Th).

[0126] Furthermore, in 3GPP, it has been proposed to match the trigger of the buffer status report (BSR) with the eNB that transmits data.

[0127] According to this, in DRAT, when the amount of data of the transmitted data is below the threshold, the data is transmitted to one set eNB (1st-eNB). When the amount of data of the transmitted data is greater than the threshold, the data is transmitted to both eNBs (1st-eNB, 2nd-eNB).

[0128] Consider the case where SPS is set for the 2nd-eNB and starts execution (is activated) with the UL split bearer set. According to DRAT, when the amount of uplink data becomes below the threshold, the UE will not transmit data to the 2nd-eNB.

[0129] There is no regulation or discussion regarding the operation when the amount of uplink data becomes below the threshold in the SPS resources set for the 2nd-eNB and the UE stops transmitting data to the 2nd-eNB.

[0130] Therefore, when the amount of uplink data is below the threshold, since data is not transmitted to the 2nd-eNB, nothing may be transmitted in the set SPS resources, and padding transmission may not be performed either.

[0131] If padding transmission is not performed, implicit release cannot be performed properly, so the UE cannot determine whether it can clear the SPS resources. Also, the eNB cannot determine whether it can release the SPS resources. Therefore, unstable operation may occur between the eNB and the UE, leading to malfunction.

[0132] FIG. 11 is a diagram for explaining problems when SPS is set when a UL split bearer is set. The 1st-eNB is taken as the MeNB, and the 2nd-eNB is taken as the SeNB. In FIG. 11, the cases where SPS is set are shown for the MeNB and the SeNB, respectively.

[0133] In step ST1001, the MeNB notifies the UE, using PDCCH, of activation with an uplink grant of the uplink SPS. The UE receives the PDCCH and activates the uplink SPS. That is, the execution of the uplink SPS is started.

[0134] From step ST1002 to step ST1007, the UE transmits uplink data to the MeNB using the uplink SPS resource set for the MeNB.

[0135] In step ST1008, the SeNB notifies the UE, using PDCCH, of activation with an uplink grant of the uplink SPS. The UE receives the PDCCH and activates the uplink SPS.

[0136] In step ST1009, the UE transmits uplink data to the SeNB using the uplink SPS resource set for the SeNB. Assume that the data volume of the transmitted data generated at the UE is equal to or greater than the threshold in the DRAT. Although not shown in the figure, the UE also transmits data to the MeNB.

[0137] Therefore, a part of the uplink data generated at the UE is transmitted to the MeNB, and the remaining uplink data is transmitted to the SeNB.

[0138] In step ST1010, consider the case where no uplink data is generated at the UE using the uplink SPS resource set for the SeNB. In this case, since the data volume of the uplink data becomes equal to or less than the threshold in the DRAT, the UE determines not to transmit uplink data to the SeNB and does not perform padding transmission either.

[0139] In steps ST1010 and ST1011, if uplink data does not continuously occur on the uplink SPS resources configured for the SeNB, similarly, since the data volume of the uplink data is below the threshold in DRAT, the UE determines not to transmit uplink data to the SeNB and also does not perform padding transmission.

[0140] Even if no uplink transmitted data has occurred continuously for the number of pre-release empty transmission times (assumed to be 2 times in FIG. 11), padding transmission is not performed. Therefore, in step ST1012, the UE cannot determine whether it can clear the SPS resources. Also, the eNB cannot determine whether it can release the SPS resources.

[0141] Therefore, unstable operations occur between the eNB and the UE, and as a result, there is a possibility of causing malfunction.

[0142] From the above, when DRAT is executed in the uplink split bearer, it is required to enable SPS and provide a high-speed and stable communication system.

[0143] In this embodiment, a method for solving such problems is disclosed.

[0144] When SPS is configured, uplink data is transmitted to both the 1st-eNB and the 2nd-eNB.

[0145] As a method for doing this, for example, when SPS is configured, no DRAT threshold is set. Alternatively, when SPS is configured, the set DRAT threshold is made invalid. By doing these, when SPS is configured, the threshold disappears or becomes invalid, and uplink data is transmitted to both the 1st-eNB and the 2nd-eNB.

[0146] A DRAT threshold for SPS may be provided. By providing a DRAT threshold for SPS, the DRAT threshold for SPS can be set to a value different from the DRAT threshold when SPS is not present, and the DRAT operation in the case of SPS can be made different from the DRAT when SPS is not present.

[0147] As another method of causing both eNBs to transmit uplink data, for example, a negative value is set as the DRAT threshold for SPS. This may be applied when both eNBs are to be transmitted in the case where the data amount of the uplink data is larger than the DRAT threshold.

[0148] Alternatively, 0 is set as the DRAT threshold for SPS. This may be applied when both eNBs are to be transmitted in the case where the data amount of the uplink data is greater than or equal to the DRAT threshold.

[0149] By doing so, when SPS is set, uplink data will be transmitted to both the 1st - eNB and the 2nd - eNB.

[0150] By using these methods, when SPS is set, uplink data will be transmitted to both the 1st - eNB and the 2nd - eNB, so padding transmission becomes possible. Therefore, implicit release becomes possible.

[0151] When SPS is set, transmitting uplink data to both the 1st - eNB and the 2nd - eNB may be determined statically in advance by a standard or the like, or may be notified to the UE together with the SPS setting. Alternatively, it may be notified to the UE together with the SPS activation.

[0152] For example, when SPS is set, it may be statically determined in advance in a standard or the like not to provide a DRAT threshold, or to invalidate the set DRAT threshold, or to set the DRAT threshold to a negative value, or to set the DRAT threshold to 0. This makes it possible to obtain a common understanding between the eNB and the UE. Also, since it is not necessary to signal this information, the signaling load can be reduced.

[0153] As another example, information for invalidating the set DRAT threshold may be provided and notified to the UE together with the SPS setting. Alternatively, a negative value or 0 may be notified to the UE as the DRAT threshold together with the SPS setting.

[0154] These notifications may be notified to the UE separately from the SPS setting. By notifying the information for invalidating the set DRAT threshold together with the SPS setting, the signaling load can be reduced. Also, since it is possible to make the timing the same as the SPS setting, the possibility of unstable operation and malfunction can be reduced. UE-specific RRC signaling may be used for these notifications.

[0155] As another example, information for invalidating the set DRAT threshold may be provided and notified to the UE together with the SPS activation. Alternatively, a negative value or 0 may be notified to the UE as the DRAT threshold together with the SPS activation.

[0156] These notifications may be notified to the UE separately from the SPS activation. By notifying the information for invalidating the set DRAT threshold together with the SPS activation, the signaling load can be reduced. Also, since it is possible to make the timing the same as the SPS activation, the possibility of unstable operation and malfunction can be reduced. L1 / L2 control signals may be used for these notifications.

[0157] Disclosed is a method for releasing the state in which uplink data is transmitted to both the 1st-eNB and the 2nd-eNB, which is set as described above.

[0158] Similar to the above, when the SPS setting is released, it is statically determined in advance by a standard or the like to release this state. Thus, the same effect as described above can be obtained.

[0159] Alternatively, information enabling the set DRAT threshold may be provided and the UE may be notified by including this information in the signaling that invalidates the SPS setting. Alternatively, the DRAT threshold to be set again may be included in the signaling that invalidates the SPS setting and the UE may be notified. Alternatively, this state may be released by the signaling that invalidates the SPS setting. Thus, the DRAT threshold can be returned to the conventional value and the same effect as described above can be obtained.

[0160] Alternatively, information enabling the set DRAT threshold may be provided and the UE may be notified by including this information in the SPS deactivation. Alternatively, the DRAT threshold to be set again may be included in the SPS deactivation and the UE may be notified. Alternatively, this state may be released by the SPS deactivation. Thus, the DRAT threshold can be returned to the conventional value and the same effect as described above can be obtained.

[0161] By using the method disclosed above, when SPS is set, uplink data will be transmitted to both the 1st-eNB and the 2nd-eNB, so padding transmission becomes possible. Therefore, implicit release becomes possible.

[0162] Thus, it is possible to reduce the possibility of unstable operation occurring between the eNB and the UE, and ultimately causing malfunction.

[0163] FIG. 12 is a diagram for explaining the case where the threshold of DRAT is set to 0 when SPS is set. When the amount of uplink data is smaller than the threshold of DRAT, it is transmitted only to the 1st-eNB, and when the amount of uplink data is equal to or greater than the threshold of DRAT, it is transmitted to both the 1st-eNB and the 2nd-eNB. The 1st-eNB is the MeNB, and the 2nd-eNB is the SeNB. The case where SPS is set for each of the MeNB and the SeNB is shown.

[0164] Since FIG. 12 is similar to FIG. 11, mainly different parts will be described.

[0165] The threshold 1103 of DRAT is set to 0.

[0166] In step ST1008, the SeNB notifies the UE of activation using the uplink grant of the uplink SPS via PDCCH. The notification of the activation includes information that sets the threshold of DRAT to 0. The UE receives the PDCCH, activates the uplink SPS, and sets the threshold of DRAT to 0.

[0167] In step ST1009, the UE transmits uplink data to the SeNB using the uplink SPS resource set for the SeNB. Since the threshold of DRAT is 0, the uplink transmission data generated at the UE can be transmitted to the SeNB. Although not shown in the figure, it is also possible to transmit data to the MeNB. Therefore, a part of the uplink data generated at the UE is transmitted to the MeNB, and the remaining uplink data is transmitted to the SeNB.

[0168] In step ST1101, consider the case where no uplink data is generated by the UE using the uplink SPS resource configured for the SeNB. In this case, since the DRAT threshold is 0, even if the generation of uplink data is 0, it is possible to transmit to the SeNB. Therefore, it is determined that padding transmission is possible, and the UE performs padding transmission to the SeNB. Thus, even when there is no uplink transmission data between the SeNB and the UE, padding transmission is possible.

[0169] From step ST1101 to step ST1102, in the case where no uplink data is continuously generated by the UE using the uplink SPS resource configured for the SeNB, similarly, since the data volume of the uplink data is equal to or greater than the DRAT threshold, the UE can transmit uplink data to the SeNB. Therefore, it is determined that padding transmission is possible, and padding transmission is performed.

[0170] If padding transmission is performed because no uplink transmission data is generated continuously for the number of times set as the pre-release empty transmission count, in step ST1012, the UE clears the SPS resource, and the eNB also releases the SPS resource.

[0171] Thereby, implicit release is normally performed between the eNB and the UE.

[0172] In the case of the method disclosed above, not only at the timing when the SPS resource is allocated, but also from the timing when the SPS is configured or activated until the release or deactivation, it is possible to transmit uplink data to both eNBs. Data will be generated.

[0173] Therefore, even when the data volume of the uplink transmission data generated by the UE is small from the timing when the SPS is configured or activated until the release or deactivation, the UE always transmits uplink data to the 2nd-eNB, so the power consumption of the UE increases.

[0174] Disclose a method for solving such problems.

[0175] Transmit uplink data to both the 1st-eNB and the 2nd-eNB only at the timing of SPS resource allocation. Transmit uplink data to both the 1st-eNB and the 2nd-eNB in accordance with the timing of SPS resource allocation.

[0176] By doing so, the period during which uplink data is transmitted to the 2nd-eNB can be shortened. Therefore, it is possible to suppress an increase in the power consumption of the UE.

[0177] According to the present embodiment as described above, when the SeNB is set to communicate with the communication terminal device using radio resources for which SPS is set, that is, radio resources allocated periodically, when the data amount of the transmission data is equal to or less than the threshold Th, the threshold Th is changed so that the transmission data is transmitted to the MeNB and the SeNB. For example, as in the present embodiment, the threshold Th is set to zero (0).

[0178] As a result, communication using SPS can also be executed at the SeNB. Therefore, it is possible to provide a communication system capable of stably performing communication operations between the MeNB and the SeNB and the UE. That is, since SPS can be enabled when DRAT is executed in the uplink split bearer, a high-speed and stable communication system can be provided.

[0179] The change of the threshold Th may be performed when the data amount of the transmission data is less than the threshold Th. Specifically, when the SeNB is set to communicate with the communication terminal device using radio resources for which SPS is set, that is, radio resources allocated periodically, when the data amount of the transmission data is less than the threshold Th, it may be configured such that the threshold Th is changed so that the transmission data is transmitted to the MeNB and the SeNB. In this case, for example, as in the present embodiment, the threshold Th is set to zero (0).

[0180] As a result, the same effects as those of the present embodiment can be obtained. Specifically, also in the SeNB, communication by SPS can be executed. Therefore, it is possible to provide a communication system capable of stably performing communication operations between the MeNB and SeNB and the UE. That is, since SPS can be enabled when DRAT is executed in the uplink split bearer, a high-speed and stable communication system can be provided.

[0181] Embodiment 2. When the method disclosed in Embodiment 1 is used, the threshold value of DRAT cannot be substantially set. Therefore, the power consumption of the UE increases.

[0182] Also, the DRAT threshold value is used in the UE when distributing uplink transmission data from the PDCP to the RLC / MAC. Therefore, in order to transmit uplink data to both eNBs in accordance with the set SPS resource allocation timing, fine time management in accordance with the SPS timing is required at the time of distributing uplink transmission data.

[0183] In such a case, malfunctions may occur due to variations in the generation timing of uplink transmission data and variations in the processing time of the PDCP.

[0184] Therefore, in order to solve the problems described in Embodiment 1, in the present embodiment, a method different from the method disclosed in Embodiment 1 is disclosed.

[0185] Support implicit release also for the 2nd-eNB. When SPS is set in the 2nd-eNB, the UE enables padding transmission to the 2nd-eNB. When SPS is set in the 2nd-eNB, even if the data amount of the uplink transmission data is smaller than the DRAT threshold value in the set SPS resource, the UE performs padding transmission to the 2nd-eNB. By doing so, implicit release becomes possible.

[0186] Padding transmission transmits a MAC PDU including at least one of a padding bit and a padding BSR as in the conventional manner. In this way, by performing the same padding transmission as in the conventional case, the control in the eNB and the UE can be simplified.

[0187] Also, when the UE continuously performs padding transmission to the 2nd-eNB for the number of times set as the pre-release empty transmission count, the UE clears the SPS setting. Also, when the 2nd-eNB continuously receives padding transmission from the UE for the number of times set as the pre-release empty transmission count, the 2nd-eNB releases the SPS resource.

[0188] FIG. 13 is a diagram for explaining a method of supporting implicit release when SPS is set for the 2nd-eNB. Let the 1st-eNB be the MeNB and the 2nd-eNB be the SeNB. The case where SPS is set for both the MeNB and the SeNB is shown. Since FIG. 13 is similar to FIGS. 11 and 12, mainly different parts will be described.

[0189] The DRAT threshold 1201 is set to an arbitrary value Th.

[0190] In step ST1008, the SeNB notifies the UE of activation using the PDCCH with an uplink grant for uplink SPS. Normal activation may be used.

[0191] In step ST1202, consider the case where uplink data does not occur in the UE with the uplink SPS resource set for the SeNB. In this case, the amount of uplink data becomes smaller than the DRAT threshold, but when SPS is set for the SeNB, padding transmission is possible for the SeNB, so the UE performs padding transmission to the SeNB.

[0192] By doing so, padding transmission becomes possible even when there is no uplink transmission data between the SeNB and the UE.

[0193] In steps ST1202 to ST1203, if no uplink data is continuously generated on the uplink SPS resources configured for the SeNB, similarly, since the data volume of the uplink data is equal to or greater than the DRAT threshold, the UE can transmit uplink data to the SeNB. Therefore, it is determined that padding transmission is possible, and padding transmission is performed.

[0194] If no uplink transmission data is generated continuously for the number of times set as the number of pre-release null transmissions and padding transmission is performed, in step ST1204, the UE clears the SPS resources, and the eNB also releases the SPS resources.

[0195] In this way, implicit release is normally performed between the SeNB and the UE.

[0196] By using the method disclosed in this embodiment, in the UL split bearer, when SPS is configured for the 2nd-eNB, it becomes possible to support implicit release.

[0197] The eNB and the UE can determine to release the SPS resources by implicit release, and can reduce the occurrence of unstable operations and malfunctions.

[0198] Therefore, when SPS is configured for the 2nd-eNB in the UL split bearer, the conventional SPS operation becomes possible.

[0199] Also, different from the method of Embodiment 1, the DRAT threshold for the 2nd-eNB can also be set to an arbitrary value. Therefore, even if a small amount of uplink transmission data is generated between when SPS is configured and when it becomes invalid, if the data volume of the uplink data is smaller than the DRAT threshold, there is no need to transmit uplink data to the 2nd-eNB. Therefore, it is possible to reduce the increase in the power consumption of the UE.

[0200] In addition, since fine-grained dynamic control is not required for setting the DRAT threshold, it is possible to suppress the occurrence of malfunction.

[0201] As described above, according to the present embodiment, when the SeNB is set to communicate with the communication terminal device using radio resources for which SPS is set, that is, periodically allocated, when the data amount of the transmission data is equal to or less than the threshold Th, the transmission data is transmitted to the MeNB, and a termination signal indicating the termination of communication using the radio resources periodically allocated is transmitted to the SeNB. Specifically, it is set to perform padding transmission.

[0202] As a result, the SeNB can terminate communication by SPS. Therefore, it is possible to provide a communication system capable of stably performing communication operations between the MeNB, the SeNB, and the UE. That is, since SPS can be enabled when DRAT is executed in the uplink split bearer, a high-speed and stable communication system can be provided.

[0203] The above setting for performing padding transmission may be performed when the data amount of the transmission data is less than the threshold Th. Specifically, when the SeNB is set to communicate with the communication terminal device using radio resources for which SPS is set, that is, periodically allocated, when the data amount of the transmission data is less than the threshold Th, the transmission data is transmitted to the MeNB, and a termination signal indicating the termination of communication using the radio resources periodically allocated is transmitted to the SeNB. Specifically, it may be configured to be set to perform padding transmission.

[0204] Accordingly, the same effects as those of the present embodiment can be obtained. Specifically, in the SeNB, communication by SPS can be terminated. Therefore, a communication system capable of stably performing communication operations between the MeNB, the SeNB, and the UE can be provided. That is, since SPS can be enabled when DRAT is executed in the uplink split bearer, a high-speed and stable communication system can be provided.

[0205] Embodiment 2 Modification 1. Another method for solving the problems shown in Embodiment 2 is disclosed. Information indicating that there is no transmission data is provided, and the UE transmits this information to the eNB using an uplink L1 / L2 control signal. For example, PUCCH is used as the uplink L1 / L2 control signal. When there is no transmission data at the timing of the set SPS, the UE maps information indicating that there is no transmission data to the PUCCH and transmits it to the eNB. The eNB receives the PUCCH from the UE at the timing of the set SPS, and by obtaining information indicating that there is no transmission data, recognizes that there is no uplink transmission data.

[0206] When the UE continuously transmits information indicating that there is no transmission data for the number of times set as the number of empty transmissions before release, the UE clears the SPS resources. When the eNB continuously receives information indicating that there is no transmission data from the UE for the number of times set as the number of empty transmissions before release, the eNB releases the SPS resources.

[0207] By doing so, it becomes possible to support implicit release.

[0208] The configuration of the PUCCH for mapping information indicating that there is no transmission data is set by the eNB and notified to the UE in advance. Examples of the configuration of the PUCCH include resources in the frequency axis direction, resources in the time axis direction, and sequences used for the reference signal (RS) used for the PUCCH.

[0209] As resources in the frequency axis direction, for example, subcarriers, resource blocks, etc. may be set. They may also be the minimum resources. The minimum resources may also be the minimum unit in transmission. The minimum unit may be, for example, 1 Physical Resource Block (abbreviation: PRB). As resources in the time axis direction, it is advisable to set the timing for transmitting PUCCH. The timing for transmitting PUCCH may be set arbitrarily, but it may also be the timing when the SPS resource is set. This enables simplified timing control in the UE and the eNB.

[0210] As the sequence for RS used for PUCCH, it may be for each cell or for each beam. By making the resources in the frequency axis direction of PUCCH different for each UE, even if PUCCH transmissions of multiple UEs occur at the same SPS resource timing, the eNB can receive them. Alternatively, as the sequence for RS used for PUCCH, it may be for each individual UE. Multiple UEs can share a PUCCH with the same resources in the frequency axis direction and the time axis direction. Even if there are PUCCHs of multiple UEs in the same resource, the eNB can receive the PUCCH of each UE by using the RS for each individual UE.

[0211] The eNB may notify the UE by including the configuration of PUCCH in the SPS setting. Alternatively, the eNB may notify the UE by including the configuration of PUCCH in the SPS activation.

[0212] As the configuration of PUCCH for mapping the information indicating the absence of transmission data, the configuration of the conventional PUCCH may be used. When there is no uplink transmission data at the set SPS resource timing, the UE maps the information indicating the absence of transmission data to the PUCCH using the configuration of the conventional PUCCH. The UE transmits the PUCCH at the timing of the set SPS resource. By using the configuration of the conventional PUCCH, the eNB does not need to separately set a PUCCH for mapping the information indicating the absence of transmission data.

[0213] As another method, information indicating that there is no transmission data may be mapped to the PUSCH. When there is no transmission data, the UE maps the information indicating that there is no transmission data to the PUSCH and transmits it to the eNB at the timing of the configured SPS.

[0214] The eNB receives the PUSCH from the UE at the timing of the configured SPS, and recognizes that there is no uplink transmission data by obtaining the information indicating that there is no transmission data.

[0215] The SPS resource has already been configured at the timing of the SPS. As the SPS resource, a resource for uplink data transmission is configured. Since the PUSCH is used for uplink data transmission, the PUSCH resource is configured.

[0216] The UE has already obtained an uplink grant for the PUSCH resource for the SPS configured by the eNB. Therefore, the UE can use the resource for PUSCH transmission for the configured SPS.

[0217] By using the PUSCH resource for the SPS that has already been configured at the timing of the SPS, there is no need to separately configure the PUCCH configuration. This enables improvement in resource utilization efficiency and reduction of signaling load.

[0218] The PUSCH resource for transmitting the information indicating that there is no transmission data may be part or all of the PUSCH resource for the SPS that is configured at the timing of the SPS.

[0219] The sequence for RS used for the PUSCH may apply the method in the case of transmitting with the aforementioned PUCCH.

[0220] As another method, the SRS (Sounding Reference Signal) may be used to indicate that there is no transmission data. A specific SRS resource for indicating the absence of transmission data is set. The minimum resource on the time axis may be one symbol. The eNB notifies the UE of the setting of the SRS resource. When there is no transmission data at the timing of the set SPS, the UE transmits the SRS using the SRS resource. When the eNB receives the SRS from the UE on the SRS resource at the timing of the SPS, it can recognize that there is no transmission data.

[0221] For the RS sequence used for SRS, the method in the case of transmitting by the aforementioned PUCCH may be applied.

[0222] As another method, an RS sequence for indicating the absence of transmission data may be provided, and the sequence may be used for the RS of PUCCH, PUSCH, or SRS. Whether to use any of PUCCH, PUSCH, and SRS may be determined statically in advance, or may be notified from the eNB to the UE. In this case, the resources for the channel or signal may be set individually for each UE.

[0223] When there is no transmission data at the timing of the set SPS, the UE transmits a predetermined channel or signal using the RS sequence. When the eNB receives a predetermined channel or signal at the timing of the SPS, it can recognize that there is no transmission data.

[0224] By using the method disclosed in this modification example, it is possible to limit the radio resources required for transmission to a minimum. Therefore, since transmission can be performed with a minimum of resources, an increase in the power consumption of the UE can be further reduced.

[0225] Also, the method disclosed in this modification example may be used only when there is no transmission data at the timing of the SPS set in the 2nd - eNB. For other set SPSs, normal padding transmission may be used.

[0226] Embodiment 3 In the UL split bearer, there may be an uplink transmission data with a data volume smaller than the DRAT threshold generated at the timing of the SPS set for the 2nd-eNB.

[0227] When the method disclosed in Embodiment 2 or Modification Example 1 of Embodiment 2 is applied, the following problems occur.

[0228] In the UE, when uplink transmission data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS set for the 2nd-eNB, although there is such uplink transmission data, no uplink transmission data will be generated for the 2nd-eNB. Therefore, the UE will perform padding transmission for the 2nd-eNB. If such padding transmission occurs continuously for the number of times set as the number of pre-release empty transmission times, due to implicit release, the SPS setting will become invalid in the UE and the 2nd-eNB, and the SPS resource will be released. That is, there may be a case where, although there is uplink transmission data at the set SPS timing, the SPS resource is released due to implicit release.

[0229] After the SPS resource is released by implicit release, in the UE, when uplink transmission data equal to or greater than the DRAT threshold is generated at the timing of the SPS set for the 2nd-eNB, the SPS set for the 2nd-eNB will not be applied.

[0230] Even if uplink transmission data is generated at the set SPS timing, the UE will not be able to perform uplink data transmission using the SPS resource.

[0231] In this way, even though uplink transmission data is generated at the timing of the configured SPS and the UE is transmitting uplink data, the SPS resources for the 2nd-eNB are released. As a result, the UE cannot transmit uplink data using the configured SPS resources to the 2nd-eNB.

[0232] FIG. 14 is a diagram for explaining the case where uplink transmission data with a data volume smaller than the DRAT threshold is generated. It shows the case when the method for supporting implicit release when SPS is configured for the 2nd-eNB, which is disclosed in Embodiment 2, is executed.

[0233] Let the 1st-eNB be the MeNB and the 2nd-eNB be the SeNB. It shows the case where SPS is configured for both the MeNB and the SeNB. Since FIG. 14 is similar to FIG. 13, mainly the different parts will be described.

[0234] In step ST1202, consider the case where uplink data with a data volume smaller than the DRAT threshold is generated in the UE using the uplink SPS resources configured for the SeNB.

[0235] In this case, in step ST1301, the UE transmits the uplink data to the MeNB.

[0236] Since no uplink transmission data is generated for the SeNB, in step ST1202, the UE will perform padding transmission to the SeNB.

[0237] From step ST1202 to step ST1203, when continuously uplink data with a data volume smaller than the DRAT threshold is generated in the UE using the uplink SPS resources configured for the SeNB, similarly, from step ST1301 to step ST1302, the UE transmits the uplink data to the MeNB. The UE performs padding transmission to the SeNB.

[0238] If there is no uplink transmission data generated continuously for the number of times set as the number of pre-release empty transmissions with respect to the SeNB and padding transmission is performed, then, by implicit release, in step ST1204, the UE clears the SPS resource and the eNB also releases the SPS resource.

[0239] However, consider the case where, after implicit release, in step ST1303, uplink data with a data volume equal to or greater than the DRAT threshold is generated at the UE on the uplink SPS resource set for the SeNB.

[0240] In this case, although not shown in the figure, the UE transmits uplink data to the MeNB.

[0241] Since uplink transmission data also occurs for the SeNB, in step ST1303, the UE will transmit uplink data to the SeNB. However, since the SPS resource has already been released, the SPS resource cannot be used for the transmission of the uplink data.

[0242] In such a case, since no resource for uplink transmission data for the SeNB is allocated to the UE, it has to start from newly transmitting a Scheduling Request (SR) signal. The UE has to transmit an SR signal to the SeNB and receive a UL grant from the SeNB.

[0243] This causes an increase in the power consumption of the UE, a decrease in the resource utilization efficiency due to an increase in PDCCH resources, and an increase in the delay of data transmission. In this embodiment, a method for solving such problems is disclosed.

[0244] When an uplink split bearer is set, do not disable the uplink SPS setting. When an uplink split bearer is set, it may not release the uplink SPS resource. When an uplink split bearer is set, it may not perform implicit release.

[0245] When the uplink split bearer is configured and the uplink SPS is configured in the 2nd - eNB, even if padding transmissions are performed continuously for the number of times set as the number of empty transmissions before release, the configured SPS resources are not cleared. The 2nd - eNB does not release the configured SPS resources even if it receives padding transmissions continuously for the number of times set as the number of empty transmissions before release.

[0246] As specific examples of methods for preventing the uplink SPS configuration from being disabled, the following two cases (1) and (2) are disclosed.

[0247] (1) Determine it statically in advance by standards or the like.

[0248] (2) Provide information indicating that the uplink SPS configuration is not to be disabled and notify the UE from the eNB.

[0249] In the method of (1) above, when the uplink split bearer is configured, it is statically determined that the uplink SPS configuration is not to be disabled. By determining this in advance by standards or the like, it becomes possible for the eNB and the UE to recognize it, so that consistent operations are possible and malfunctions can be reduced.

[0250] In the method of (2) above, by notifying the UE from the eNB of the information indicating that the uplink SPS configuration is not to be disabled, it becomes possible to dynamically set that the uplink SPS configuration is not to be disabled when the uplink split bearer is configured. Thereby, flexible operation becomes possible according to the communication situation and the load situation.

[0251] As the information indicating that the uplink SPS configuration is not to be disabled in the method of (2) above, the above - mentioned number of empty transmissions before UL release may be used. As the number of empty transmissions before release, a value indicating that the SPS configuration is not to be disabled is set. Alternatively, as the number of empty transmissions before release, a value indicating infinity is set. It may be newly provided separately from the existing values.

[0252] Information indicating not to disable the uplink SPS setting in the method of (2) above may be notified from the eNB to the UE. The eNB that notifies may be the 1st-eNB or the 2nd-eNB. For example, when notifying the UE from the 2nd-eNB, it may be directly notified from the 2nd-eNB to the UE, or it may be notified from the 2nd-eNB to the UE via the 1st-eNB. For the notification of information between eNBs, X2 signaling may be used. Alternatively, S1 signaling may be used via the MME.

[0253] As specific examples of the signaling method for notifying the UE of this information from the eNB, the following three (1) to (3) are disclosed.

[0254] (1) RRC signaling. For example, it may be notified including in the signaling for the setting of the SPS configuration.

[0255] (2) MAC signaling. For example, a MAC CE (Control Element) including this information may be provided and notified by MAC signaling.

[0256] (3) L1 / L2 signaling. For example, PDCCH or EPDCCH. For example, it may be notified including in the SPS activate.

[0257] In such a method, the eNB notifies the UE of information indicating not to disable the uplink SPS setting. The UE that receives this information does not disable the uplink SPS setting. When an uplink split bearer is set and the uplink SPS is set in the 2nd-eNB, the UE does not perform an implicit release and does not clear the set SPS resources even if padding transmissions are performed continuously for the number of times set as the number of pre-release empty transmissions.

[0258] FIG. 15 is a diagram for explaining a method of preventing the setting of the uplink SPS from being disabled. The case of a method of including information indicating that the setting of the uplink SPS is not to be disabled in the SPS activation and notifying it is shown.

[0259] The 1st - eNB is set as the MeNB, and the 2nd - eNB is set as the SeNB. The case where SPS is set in both the MeNB and the SeNB is shown. Since FIG. 15 is similar to FIG. 14, mainly the different parts will be described.

[0260] In step ST1008, the SeNB notifies the UE of activation using the uplink grant of the uplink SPS via the PDCCH. The activation includes information indicating that the setting of the uplink SPS is not to be disabled.

[0261] The UE that has received the activation of the SPS from the SeNB executes the SPS with the set resources and does not disable the setting of the uplink SPS. Even if the UE performs pre - determined number of padding transmissions for the SeNB, neither the eNB nor the UE performs implicit release, and it is set so as not to disable the setting of the SPS.

[0262] In step ST1202, consider the case where uplink data with a data volume smaller than the DRAT threshold occurs at the UE at the timing of the SPS set for the SeNB.

[0263] In this case, in step ST1301, the UE transmits the uplink data to the MeNB.

[0264] Since no uplink transmission data occurs for the SeNB, in step ST1202, the UE will perform padding transmission for the SeNB.

[0265] From step ST1202 to step ST1203, if no uplink data with a data volume smaller than the DRAT threshold occurs continuously at the timing of the SPS set for the SeNB, similarly, from step ST1301 to step ST1302, the UE performs uplink data transmission to the MeNB. The UE performs padding transmission to the SeNB.

[0266] Even if no uplink transmission data occurs continuously for the number of times set as the pre-release empty transmission count for the SeNB and padding transmission is performed, according to the setting that does not invalidate the uplink SPS setting, in step ST1204, the UE does not clear the SPS resource. The eNB also does not release the SPS resource. In step ST1204, implicit release is not performed and the SPS resource is not released.

[0267] Therefore, after padding transmission is continuously performed for the number of times set as the pre-release empty transmission count for the SeNB, if uplink data with a data volume equal to or greater than the DRAT threshold occurs at the UE at the timing of the SPS set for the SeNB in step ST1204, in step ST1401, the UE can perform uplink data transmission using the set SPS resource for the SeNB.

[0268] By using the method disclosed in this embodiment, it is possible to eliminate the situation where, although uplink transmission data occurs at the set SPS timing and the UE is transmitting uplink data, the SPS resource for the 2nd-eNB is released. Therefore, it is possible to eliminate the situation where uplink data cannot be transmitted to the 2nd-eNB when uplink data occurs with the set SPS resource, and the start from the transmission of the SR signal is forced.

[0269] As a result, it is possible to suppress an increase in the power consumption of the UE, a decrease in the resource utilization efficiency due to an increase in PDCCH resources, and an increase in the delay of data transmission.

[0270] As described above, in this embodiment, when the UE receives information indicating that the setting of the uplink SPS is not to be invalidated, the UE stops releasing the SPS resource, which is a radio resource allocated by the SPS. The information indicating that the setting of the uplink SPS is not to be invalidated corresponds to release stop information indicating that the release of the SPS resource is to be stopped. That is, when the UE receives the release stop information, the UE stops releasing the SPS resource.

[0271] This prevents the situation where uplink data cannot be transmitted to the SeNB when uplink data occurs on the set SPS resource, and eliminates the situation where the start of the transmission of the SR signal is forced. Therefore, it is possible to suppress an increase in the power consumption of the UE, a decrease in the resource utilization efficiency due to an increase in the PDCCH resource, and an increase in the delay of data transmission.

[0272] Embodiment 4. In the method disclosed in Embodiment 3, at the timing of the set SPS, even when there is no actual transmission data, implicit release is not performed, and the SPS resource is not released.

[0273] If the SPS resource is not released, the 2nd-eNB continues to allocate the SPS resource to the UE at the timing of the SPS.

[0274] Thus, continuously allocating the PUSCH resource to a UE that has no transmission data is wasteful and reduces the resource utilization efficiency. In this embodiment, a method for solving such a problem is disclosed.

[0275] A timer for a period during which the setting of the SPS is not to be invalidated is provided. The eNB sets a period during which the setting of the SPS is not to be invalidated and notifies the UE.

[0276] For example, when a setting is made not to disable the uplink SPS setting, the aforementioned timer is used to start the implicit release function. The eNB notifies the UE of the period during which the SPS setting is not disabled, together with information indicating that the SPS setting is not disabled. When the setting of not disabling the uplink SPS setting is set, the UE starts the timer, and when the period during which the SPS setting is not disabled has elapsed, the UE starts implicit release and stops the timer. By doing so, when padding transmissions are continuously performed for the number of times set as the number of empty transmissions before release, implicit release is performed and the uplink SPS resources are released.

[0277] The period during which the SPS setting is not disabled may be time, the number of radio frames, the number of subframes, the number of slots, and the number of symbols. The period during which the SPS setting is not disabled may be a positive integer multiple of the set SPS timing interval. The period during which the SPS setting is not disabled may be statically determined in advance by a standard or the like.

[0278] As another method, it may be set to start implicit release when the number of padding transmissions continues for a predetermined number of times. The predetermined continuous number of padding transmissions disclosed in this embodiment may be made different from the conventional number of empty transmissions before release.

[0279] Specifically, when a parameter representing the predetermined continuous number of padding transmissions is "implicitReleaseAfter_B" and a parameter representing the conventional number of empty transmissions before release is "implicitReleaseAfter", implicitReleaseAfter_B > implicitReleaseAfter may be set.

[0280] Alternatively, implicitReleaseAfter_B = n (n is a positive integer) × implicitReleaseAfter may be set.

[0281] By doing so, it becomes possible to start implicit release according to the period during which there is no uplink transmission data. It becomes possible to set the period during which the uplink SPS setting is invalidated according to the occurrence status of the uplink transmission data.

[0282] By using the method disclosed in this embodiment, it is possible to eliminate the state where implicit release is not always performed while the setting of the uplink SPS is set not to be invalidated.

[0283] Therefore, it becomes unnecessary to reserve SPS resources for a long time, and it becomes possible to reduce the waste of PUSCH resources. As a result, it becomes possible to improve the resource utilization efficiency.

[0284] Embodiment 4 Variation 1. Another method for solving the problems shown in Embodiment 4 is disclosed. Information indicating the start of implicit release is provided and notified from the eNB to the UE. For example, in a state where it is set not to invalidate the uplink SPS setting, information indicating the start of implicit release is notified from the eNB to the UE. By notifying this information, both the eNB and the UE resume implicit release. By doing so, when padding transmissions occur continuously from the UE to the eNB for the number of times set as the number of empty transmissions before release, implicit release is executed and the uplink SPS setting becomes invalid.

[0285] By notifying the UE from the eNB of information indicating the start of implicit release, it becomes possible to start implicit release at an arbitrary timing. As a result, flexible operation becomes possible according to the communication status and the load status.

[0286] As the information indicating the start of implicit release, the above-mentioned number of empty transmissions before UL release may be used. An existing value may be set as the number of empty transmissions before release. When the number of empty transmissions before release is set, implicit release is started.

[0287] Information indicating the start of implicit release may be notified from the eNB to the UE. The eNB that notifies may be the 1st-eNB or the 2nd-eNB. For example, when notifying the UE from the 2nd-eNB, it may be directly notified from the 2nd-eNB to the UE, or it may be notified from the 2nd-eNB to the UE via the 1st-eNB. X2 signaling may be used for the notification of information between eNBs. Alternatively, S1 signaling may be used via the MME.

[0288] As specific examples of the signaling method for notifying the UE from the eNB of the information indicating the start of implicit release, the following three (1) to (3) are disclosed.

[0289] (1) RRC signaling.

[0290] (2) MAC signaling. For example, a MAC CE including information indicating the start of implicit release may be provided and notified by MAC signaling.

[0291] (3) L1 / L2 signaling. For example, it may be notified by PDCCH or EPDCCH.

[0292] By using the method disclosed in this modification example, the same effects as the method disclosed in Embodiment 4 can be obtained.

[0293] Also, since it is possible to start implicit release at any timing, flexible setting of SPS resources becomes possible. Therefore, it is possible to further improve the usage efficiency of PUSCH resources.

[0294] As described above, in this modification example, when the UE receives information indicating the start of implicit release, the UE resumes the release of the SPS resource. The information indicating the start of implicit release corresponds to release resume information indicating the resume of SPS release. That is, when the UE receives the release resume information, the UE resumes the release of the SPS resource.

[0295] As a result, the same effects as those in Embodiment 4 can be obtained. Specifically, it is possible to eliminate the state where implicit release is not always performed while the setting of the uplink SPS is not set to be invalid. As a result, it is not necessary to reserve the SPS resource for a long time, so it is possible to reduce the waste of the PUSCH resource. Therefore, it is possible to improve the resource utilization efficiency.

[0296] Embodiment 4 Modification Example 2. Another method for solving the problem shown in Embodiment 4 is disclosed. Information indicating that the setting of the uplink SPS is to be invalidated is provided and notified from the eNB to the UE. For example, in a state where it is set that the setting of the uplink SPS is not to be invalidated, information indicating that the setting of the uplink SPS is to be invalidated is notified from the eNB to the UE. The eNB determines whether to invalidate the setting of the uplink SPS. When the eNB decides to invalidate the setting of the uplink SPS, the eNB notifies the UE of the information indicating that the setting of the uplink SPS is to be invalidated and invalidates the setting of the uplink SPS. The UE invalidates the setting of the uplink SPS by receiving the information indicating that the setting of the uplink SPS is to be invalidated from the eNB. At this time, the setting of the uplink SPS is invalidated without performing implicit release.

[0297] By notifying the UE from the eNB of the information indicating that the setting of the uplink SPS is to be invalidated, it is possible to invalidate the setting of the uplink SPS at an arbitrary timing. As a result, flexible operation is possible according to the communication situation and the load situation.

[0298] As information indicating disabling the uplink SPS setting, the above-mentioned number of pre-release empty transmissions for UL may be used. As the number of pre-release empty transmissions, an existing value may be set. When the number of pre-release empty transmissions is set, it may be configured to indicate disabling the uplink SPS setting.

[0299] The information indicating disabling the uplink SPS setting may be notified from the eNB to the UE. The eNB for notification may be the 1st-eNB or the 2nd-eNB. For example, when notifying the UE from the 2nd-eNB, it may be directly notified from the 2nd-eNB to the UE, or notified from the 2nd-eNB to the UE via the 1st-eNB. X2 signaling may be used for notification of information between eNBs. Alternatively, S1 signaling may be used via the MME.

[0300] As specific examples of signaling methods for notifying the UE from the eNB of the information indicating disabling the uplink SPS setting, the following three cases (1) to (3) are disclosed.

[0301] (1) RRC signaling.

[0302] (2) MAC signaling. For example, a MAC CE including information indicating disabling the uplink SPS setting may be provided and notified by MAC signaling.

[0303] (3) L1 / L2 signaling. For example, it may be notified by PDCCH or EPDCCH.

[0304] FIG. 16 is a diagram for explaining a method of using information indicating disabling the uplink SPS setting. The 1st-eNB is taken as the MeNB, and the 2nd-eNB is taken as the SeNB. It shows the case where SPS is set in both the MeNB and the SeNB. Since FIG. 16 is similar to FIG. 15, mainly different parts will be described.

[0305] In step ST1008, the SeNB notifies the UE, using PDCCH, of the activation of the uplink grant of the uplink SPS. The activation includes information indicating that the setting of the uplink SPS is not to be disabled.

[0306] From step ST1202 to step ST1203, even when there is no uplink transmission data generated continuously for the number of times set as the pre-release empty transmission count at the SeNB and padding transmission is performed, according to the setting that the setting of the uplink SPS is not to be disabled, the UE does not clear the SPS resources. The eNB also does not release the SPS resources. Implicit release is not performed and the SPS resources are not released.

[0307] In step ST1501, the SeNB sets information indicating that the setting of the uplink SPS is to be disabled and notifies the UE. The eNB disables the setting of the uplink SPS by notifying the information indicating that the setting of the uplink SPS is to be disabled, and the UE disables the setting of the uplink SPS by receiving the information indicating that the setting of the uplink SPS is to be disabled.

[0308] Since the setting of the uplink SPS is disabled, at step ST1204 which is the subsequent SPS timing, the set SPS resources are released. As a result, the eNB can allocate the SPS resources to other UEs.

[0309] As specific examples of the method for the eNB to determine whether to disable the setting of the uplink SPS, the following six cases (1) to (6) are disclosed.

[0310] (1) The period from the setting of the SPS.

[0311] (2) The period after setting not to disable the setting of the SPS.

[0312] (3) The continuous reception count of padding transmissions.

[0313] (4) The load amount at the self eNB.

[0314] (5) Communication quality with the UE.

[0315] (6) Uplink transmission data generation status with respect to the 1st - eNB.

[0316] In the method of (1) above, when a predetermined period has elapsed since the setting of the uplink SPS, it is determined to invalidate the setting of the uplink SPS. The predetermined period may be time, the number of radio frames, the number of sub - frames, the number of slots, and the number of symbols. The predetermined period may be a positive integer multiple of the set timing interval of the SPS.

[0317] In the method of (2) above, when a predetermined period has elapsed since setting not to invalidate the setting of the uplink SPS, it is determined to invalidate the setting of the uplink SPS.

[0318] In the method of (3) above, when padding transmissions are received continuously for a predetermined number of times, it is determined to invalidate the setting of the uplink SPS. The predetermined number of times of receiving padding transmissions may be the number of pre - release empty transmission times described above. Or, it may be a value larger than the number of pre - release empty transmission times.

[0319] In the method of (4) above, it is determined using the load of the self - eNB. When the load is equal to or greater than a predetermined value, it is determined to invalidate the setting of the SPS. When the load is lower than the predetermined value, it is determined not to invalidate the setting of the SPS. When the load is higher than the predetermined value, the resources allocated for the SPS are released so that they can be allocated to other UEs, thereby reducing the resource shortage that occurs when the load is high.

[0320] In the method of (5) described above, it is determined using the communication quality with the UE. When the communication quality is lower than a predetermined value, it is determined to invalidate the SPS setting. When the communication quality is equal to or higher than the predetermined value, it is determined not to invalidate the SPS setting. There may be a case where the reason for the low communication quality is that the communication quality of the resources already set for SPS is poor. In such a case, the communication quality can be improved by reallocating the resources for SPS. Therefore, when the communication quality is low, it is advisable to invalidate the SPS setting and make it possible to set SPS again as needed. By doing so, the communication quality can be improved. Also, since the resources with poor communication quality can be released early, the usage efficiency of the resources can be improved.

[0321] In the method of (6) described above, the 2nd-eNB recognizes the generation status of the uplink transmission data to the 1st-eNB and determines whether to invalidate the uplink SPS setting.

[0322] As specific examples of the method for the 2nd-eNB to recognize the generation status of the uplink transmission data to the 1st-eNB, the following two cases of (6-1) and (6-2) are disclosed.

[0323] (6-1) The 2nd-eNB acquires information regarding the generation of uplink transmission data from the 1st-eNB.

[0324] The 1st-eNB may notify the 2nd-eNB whether uplink transmission data to its own eNB (1st-eNB) has been generated at the timing of the SPS set for the 2nd-eNB.

[0325] The 2nd-eNB may notify the 1st-eNB in advance of the timing of the SPS set for its own eNB. Thereby, the 1st-eNB can recognize whether it has received uplink transmission data from the UE at the timing of the SPS set for the 2nd-eNB. When the 1st-eNB receives uplink transmission data from the UE at the timing of the SPS set for the 2nd-eNB, it determines that uplink transmission data has occurred. When the 1st-eNB does not receive the uplink transmission data from the UE, it determines that uplink transmission data has not occurred.

[0326] The 1st-eNB notifies the 2nd-eNB of the presence or absence of uplink transmission data for its own eNB. It may notify only when there is no uplink transmission data for its own eNB, or only when there is.

[0327] By receiving information on the presence or absence of uplink transmission data for its own eNB, the 2nd-eNB can determine whether uplink transmission data exists for the 1st-eNB. The 2nd-eNB uses the information on the presence or absence of uplink transmission data for its own eNB to decide whether to invalidate the uplink SPS setting.

[0328] For example, when information indicating that there is no uplink transmission data for the 1st-eNB is received continuously for a predetermined number of times, it may be determined to invalidate the uplink SPS setting.

[0329] The 2nd-eNB may notify the 1st-eNB of which bearer the 2nd-eNB has set SPS for.

[0330] The 1st-eNB may determine whether uplink transmission data has occurred on the bearer.

[0331] Thereby, when SPS is set for a specific bearer, it is effective because the bearer can be identified.

[0332] The 1st-eNB may notify the 2nd-eNB of the number of consecutive times when no uplink transmission data has occurred.

[0333] Alternatively, the 2nd-eNB may notify the 1st-eNB of the number of consecutive times in advance. The 1st-eNB counts the number of times it fails to receive uplink transmission data at the timing of the SPS set for the 2nd-eNB, and when the number of consecutive times is reached, notifies the 2nd-eNB to that effect.

[0334] A new message for requesting invalidation of the SPS setting may be provided between eNBs. For example, the 1st-eNB counts the number of times it fails to receive uplink transmission data at the timing of the SPS set for the 2nd-eNB, and when the number of consecutive times is reached, notifies the 2nd-eNB of a message requesting invalidation of the SPS setting.

[0335] The 2nd-eNB that receives the message requesting invalidation of the SPS setting may decide to invalidate the uplink SPS setting.

[0336] To notify the above information between eNBs, X2 signaling or S1 signaling may be used. Notification may be made by X2 signaling or by S1 signaling via the MME.

[0337] (6-2) The 2nd-eNB measures and detects the uplink power at the 1st-eNB at the timing of the SPS.

[0338] The 1st-eNB may notify the 2nd-eNB in advance of the uplink carrier frequency and bandwidth of the 1st-eNB. When the 1st-eNB also sets the SPS at the timing of the SPS set for the 2nd-eNB, the SPS resource may be notified to the 2nd-eNB.

[0339] The 2nd-eNB measures the uplink power at the set SPS timing using the carrier frequency and bandwidth of the 1st-eNB. When the 1st-eNB has set SPS as described above, the uplink power in the SPS resource may be measured.

[0340] As the uplink power, it is advisable to measure the Received Signal Strength Indicator (abbreviation: RSSI), IoT (Interference over Thermal noise), etc.

[0341] If the measured uplink power is higher than a predetermined threshold, it is determined that data has been transmitted by the 1st-eNB. If it is lower than the predetermined threshold, it is determined that data has not been transmitted by the 1st-eNB.

[0342] If it is determined that data has not been transmitted by the 1st-eNB, the 2nd-eNB may decide to invalidate the uplink SPS setting.

[0343] The method disclosed in this modification example for the eNB to determine whether to invalidate the uplink SPS setting can also be applied to the method disclosed in Modification Example 1 of Embodiment 4 for determining to start implicit release.

[0344] By using the method disclosed in this modification example, the same effects as those of the method disclosed in Modification Example 1 of Embodiment 4 can be obtained.

[0345] Also, it is not necessary to perform implicit release, and it becomes possible to immediately invalidate the SPS setting and release the SPS resource. Therefore, it is possible to further improve the usage efficiency of the PUSCH resource.

[0346] Embodiment 5. Disclose another method for solving the problems shown in Embodiment 4. Make the padding transmission when there is no uplink transmission data at the set SPS timing different from the padding transmission when there is uplink transmission data at the set SPS timing.

[0347] When there is no uplink transmission data, the UE performs padding transmission when there is no uplink transmission data. When there is uplink transmission data, the UE performs padding transmission when there is uplink transmission data. By receiving different padding transmissions, the eNB determines the presence or absence of uplink transmission data from the UE at the set SPS timing. When the eNB receives the padding transmission when there is no uplink transmission data, it determines that there is no uplink transmission data and performs implicit release. When the eNB receives the padding transmission when there is uplink transmission data, it determines that there is uplink transmission data and does not count it as the padding transmission when there is no uplink transmission data. Alternatively, it may not perform uplink implicit release.

[0348] Figures 17 and 18 are diagrams for explaining a method of making the padding transmission when there is no uplink transmission data different from the padding transmission when there is uplink transmission data. Let the 1st-eNB be the MeNB and the 2nd-eNB be the SeNB. The case where the data volume of the uplink transmission data is below the DRAT threshold (Th) is shown. The case where SPS is set for the SeNB is shown.

[0349] Figure 17 shows the case where there is no uplink transmission data at the SPS timing set for the SeNB. Figure 18 shows the case where there is uplink transmission data at the SPS timing set for the SeNB. Let the padding transmission when there is no uplink transmission data be "padding (A) transmission". Let the padding transmission when there is uplink transmission data be "padding (B) transmission".

[0350] Since Figures 17 and 18 are similar to Figure 9, mainly the different parts will be described.

[0351] As shown in FIG. 17, when there is no uplink transmission data, the UE 905 performs padding (A) transmission to the SeNB 902 at the timing of the SPS set for the SeNB 902, as indicated by the arrow “1601”. Since there is no uplink transmission data, no uplink data is transmitted from the UE 905 to the MeNB 901.

[0352] As shown in FIG. 18, when there is uplink transmission data, the UE 905 performs padding (B) transmission to the SeNB 902 at the timing of the SPS set for the SeNB 902, as indicated by the arrow “1602”. Since there is uplink transmission data, uplink data is transmitted from the UE 905 to the MeNB 901, as indicated by the arrow “1603”.

[0353] FIGS. 19 and 20 are diagrams for explaining a method of differentiating between padding transmission when there is no uplink transmission data and padding transmission when there is uplink transmission data. The padding transmission when there is no uplink transmission data is referred to as “padding (A) transmission”. The padding transmission when there is uplink transmission data is referred to as “padding (B) transmission”.

[0354] The 1st - eNB is the MeNB and the 2nd - eNB is the SeNB. The case where SPS is set for both the MeNB and the SeNB is shown. Since FIG. 19 is similar to FIG. 13 and FIG. 20 is similar to FIG. 15, mainly the different parts will be described.

[0355] FIG. 19 shows the padding (A) transmission when there is no uplink transmission data.

[0356] In step ST1008, the SeNB notifies the UE to activate with an uplink grant of the uplink SPS using the PDCCH.

[0357] The UE that has received the activation of the SPS from the SeNB executes the SPS with the set resources.

[0358] In step ST1701, consider the case where no uplink data is generated at the UE at the timing of the SPS set for the SeNB.

[0359] In this case, in step ST1701, the UE performs padding (A) transmission to the SeNB when there is no uplink transmission data.

[0360] From step ST1701 to step ST1702, when no uplink data is continuously generated at the UE at the timing of the SPS set for the SeNB, similarly, the UE performs padding (A) transmission to the SeNB.

[0361] When no uplink transmission data is generated continuously for the number of times set as the pre-release empty transmission count for the SeNB and padding (A) transmission is performed, implicit release is performed.

[0362] By implicit release, in step ST1204, the eNB releases the set SPS resources. In step ST1204, the UE clears the set SPS resources.

[0363] Figure 20 shows padding (B) transmission when there is uplink transmission data.

[0364] In step ST1008, the SeNB notifies the UE of activation using the PDCCH with an uplink grant for the uplink SPS.

[0365] The UE that has received the activation of the SPS from the SeNB executes the SPS with the set resources.

[0366] In step ST1801, consider the case where uplink data is generated at the UE at the timing of the SPS configured for the SeNB. Here, assume that the generated uplink data is data with a data volume smaller than the DRAT threshold. In this case, the uplink data is transmitted to the MeNB, but not to the SeNB. Apply the method disclosed in Embodiment 3, and perform padding transmission for the SeNB.

[0367] However, in the method disclosed in this embodiment, in step ST1801, when there is uplink transmission data for the SeNB at the UE, the UE performs padding (B) transmission.

[0368] From step ST1801 to step ST1802, when uplink data is continuously generated at the UE at the timing of the SPS configured for the SeNB, but the data volume is smaller than the DRAT threshold and no uplink data is transmitted to the SeNB, similarly, the UE performs padding (B) transmission for the SeNB.

[0369] Even if padding (B) transmission is continuously performed for the SeNB for the number of times set as the number of pre-release empty transmissions, implicit release is not performed.

[0370] Therefore, in step ST1204, the eNB does not release the configured SPS resource, and in step ST1204, the UE does not clear the configured SPS resource.

[0371] Therefore, after padding (B) transmission is continuously performed for the SeNB for the number of times set as the number of pre-release empty transmissions, in step ST1204, when uplink data with a data volume equal to or greater than the DRAT threshold is generated at the UE at the timing of the SPS configured for the SeNB, in step ST1401, the UE can transmit the uplink data to the SeNB using the configured SPS resource.

[0372] By doing so, it is possible to prevent implicit release from occurring even though there is uplink transmission data. When uplink transmission data equal to or greater than the DRAT threshold occurs in the UE, it becomes possible to use the SPS resources set in the SeNB for transmitting the uplink data.

[0373] As described above, by differentiating between padding transmission when there is no uplink transmission data and padding transmission when there is uplink transmission data, the eNB can determine the presence or absence of uplink transmission data from the UE at the timing of the set SPS.

[0374] When the eNB receives padding transmission when there is no uplink transmission data, it can determine that there is no uplink transmission data. Since there is no uplink transmission data from the UE, the eNB may count it as padding transmission when performing implicit release.

[0375] When the eNB receives padding transmission when there is uplink transmission data, it can determine that there is uplink transmission data. Since there is uplink transmission data from the UE, the eNB should not count it as padding transmission when performing implicit release.

[0376] By only counting the padding transmission when there is no uplink transmission data from the UE, when the padding transmission when there is actually no uplink transmission data from the UE is continuously performed the number of times set as the number of pre-release empty transmissions, it becomes possible to perform implicit release.

[0377] Disclose a method of differentiating between padding transmission when there is no uplink transmission data and padding transmission when there is uplink transmission data.

[0378] Regarding the padding transmission when there is no uplink transmission data, it is preferable to transmit a MAC PDU including at least one of a padding bit and a padding BSR, which is the conventional padding transmission shown in Embodiment 1.

[0379] Make the padding transmission when there is uplink transmission data different from the conventional padding transmission.

[0380] In the padding transmission when there is uplink transmission data, it is advisable to make the processing of the MAC layer different from the conventional one. As specific examples of the method for constructing a MAC PDU different from the MAC PDU of the conventional padding transmission, the following three (1) to (3) are disclosed.

[0381] (1) Provide a new MAC CE (Control Element).

[0382] (2) Set a specific value for the padding bit.

[0383] (3) Set a specific value for the header.

[0384] As the method of (1) above, it is advisable to provide a MAC CE indicating that it is a padding transmission when there is uplink transmission data.

[0385] For example, provide a MAC CE indicating the presence or absence of transmission. In addition to at least one of the conventional padding bit and the padding BSR, a MAC CE indicating the presence or absence of transmission may be included. It may be a MAC CE indicating that there is transmission.

[0386] Alternatively, a MAC CE indicating the type of padding transmission may be provided. It may be a MAC CE indicating whether it is a padding transmission when there is no uplink transmission data or a padding transmission when there is uplink transmission data.

[0387] Alternatively, a MAC CE indicating the presence or absence of implicit release may be provided. This padding transmission including this MAC CE indicates whether to perform implicit release or not to perform implicit release.

[0388] By doing so, it can be made different from the conventional padding transmission.

[0389] As the method of (2) above, a specific value indicating that it is a padding bit when there is uplink transmission data may be set for the padding bit. Conventionally, whether it is a padding bit or not is determined by the header, so the padding bit could be anything. Here, a specific value indicating that it is padding when there is uplink transmission data is newly set. The eNB can recognize whether it is padding transmission when there is uplink transmission data by demodulating the padding bit.

[0390] As the method of (3) above, a value indicating the presence or absence of uplink transmission data may be provided in the header. For example, a value indicating the presence or absence of uplink transmission data is added as a specific value to the header of the padding bit. Thereby, in the case of a header indicating that there is transmission data, it can be recognized that it is padding transmission when there is uplink transmission data.

[0391] Alternatively, the specific value may be added to the header of the padding BSR. Thereby, the same effect can be obtained.

[0392] Alternatively, the specific value may be added to the header of the MAC CE indicating that it is padding transmission when there is uplink transmission data. Thereby, it becomes possible to determine whether there is uplink transmission data both in the MAC CE and the header. Therefore, it is possible to reduce malfunction.

[0393] In this way, as padding transmission when there is uplink transmission data, it is possible to make it different from the conventional padding transmission by making the processing of the MAC layer different from the conventional one.

[0394] As another method, as padding transmission when there is uplink transmission data, the processing of the PHY layer may be made different from the conventional one.

[0395] For example, make the reference signal used for PUSCH that performs padding transmission when there is uplink transmission data different from the reference signal used for PUSCH that performs padding transmission when there is no conventional uplink transmission data.

[0396] Alternatively, at least one of the resources on the frequency axis and the resources on the time axis to which PUSCH that performs padding transmission when there is uplink transmission data is mapped may be made different from at least one of the resources on the frequency axis and the resources on the time axis to which PUSCH that performs padding transmission when there is no conventional uplink transmission data is mapped.

[0397] At least one of the resources on the frequency axis and the resources on the time axis may be made different within at least one of the resources on the frequency axis and the resources on the time axis allocated as SPS resources. That is, both the resource to which PUSCH that performs padding transmission when there is uplink transmission data is mapped and the resource to which PUSCH that performs padding transmission when there is no uplink transmission data is mapped will be within the resources allocated as SPS resources. As a result, it is not necessary to use resources outside the set SPS resources, so an increase in the required resources can be suppressed.

[0398] As a method of making a difference within the SPS resources, the resources on the time axis may be made different. For example, make a difference for each slot. It may also be for each symbol. Alternatively, the resources on the frequency axis may be made different. For example, make a difference for each subcarrier. It may also be for each resource block.

[0399] In addition to the SPS resources, radio resources (resources on the frequency axis - resources on the time axis) may be provided. For example, when there is no transmission data, padding transmission is performed using the SPS resources. When there is transmission data, padding transmission is performed using separately configured radio resources. As a result, for conventional padding transmission, there is no need to change the mechanism, making control easier. The separately configured radio resources may be used by multiple UEs. Specifically, multiplexing may be performed. For example, time multiplexing, frequency multiplexing, code multiplexing, etc. may be performed. Alternatively, collision-based sharing may also be used. The eNB may decompose for each UE using the RS of the PUSCH transmitted by the UE.

[0400] As another method, depending on the presence or absence of uplink transmission data, it may be switched whether to perform transmission using the L1 / L2 control signal or padding transmission. For example, when there is uplink transmission data, transmission using the L1 / L2 control signal is performed instead of padding transmission, and when there is no uplink transmission data, conventional padding transmission is performed. The eNB can recognize the presence or absence of uplink transmission data depending on whether it is received by the L1 / L2 control signal or by conventional padding transmission. For the L1 / L2 control signal in the case where there is uplink transmission data, the method disclosed in Modification Example 1 of Embodiment 2 may be used.

[0401] By doing so, the 2nd-eNB can recognize the presence or absence of the UE's transmission data. When there is no uplink transmission data at the timing of the SPS set for the 2nd-eNB, it becomes possible to execute implicit release. When there is uplink transmission data in the SPS resources for the 2nd-eNB, it is possible to prevent implicit release from being executed.

[0402] Therefore, as disclosed in Embodiment 3, when considering the case where there is uplink transmission data at the timing of the SPS set for the 2nd-eNB and preventing implicit release from being executed, the long-term reservation of SPS resources becomes unnecessary. As a result, it becomes possible to improve the usage efficiency of PUSCH resources.

[0403] In this embodiment, DC is set, and a method of varying padding transmission is disclosed according to whether there is uplink transmission data at the timing of the SPS set in the 2nd-eNB. Not limited to this, when different padding transmissions are to be sent from one eNB, the method disclosed in this embodiment may be applied.

[0404] For example, the UE measures the time change in the amount of uplink transmission data generated, and uses the measurement result to derive the probability that uplink transmission data will be generated at the uplink transmission timing. In other words, the UE predicts the probability that uplink transmission data will be generated at the uplink transmission timing using the measurement result of the time change in the amount of uplink transmission data generated. Statistical processing may be performed to derive the probability that uplink transmission data will be generated at the uplink transmission timing.

[0405] Padding transmission may be varied according to the probability that uplink transmission data will be generated at the uplink transmission timing. The measurement of the time change in the amount of uplink transmission data generated may be performed for each bearer. Alternatively, it may be performed for each content or for each application.

[0406] The UE determines whether the probability that uplink transmission data will be generated at the uplink transmission timing is equal to or greater than a predetermined threshold. The threshold may be determined in advance as a system, or may be set by the eNB and notified from the eNB. Padding transmission is varied according to whether the probability that uplink transmission data will be generated is equal to or greater than a predetermined threshold.

[0407] When no uplink transmission data is actually generated at the set uplink SPS timing, the UE will perform padding transmission. At this time, when the probability that uplink transmission data will be generated is equal to or greater than the threshold, padding (B) transmission is performed. When the probability that uplink transmission data will be generated is not equal to or greater than the threshold, that is, when the probability that uplink transmission data will be generated is less than the threshold, padding (A) transmission is performed.

[0408] The eNB does not release the SPS resource even if it receives the number of times set as the number of empty transmissions before release from the UE and even if it continuously receives padding (B). Also, the UE does not clear the set SPS resource even if it transmits padding (B) continuously for the number of times set as the number of empty transmissions before release to the eNB. By doing so, when the probability of uplink transmission data generation is high, it is possible not to release the SPS resource.

[0409] For example, when uplink transmission data is originally generated but, due to some delay, uplink transmission data does not happen to be generated at that uplink transmission timing by chance, it is possible not to release the SPS resource. Therefore, when the generation of uplink transmission data continues, it is possible not to release the SPS resource, and it becomes possible to transmit uplink data using the SPS resource at the next SPS timing.

[0410] When the eNB receives padding (A) continuously for the number of times set as the number of empty transmissions before release from the UE, it releases the SPS resource. Also, when the UE transmits padding (A) continuously for the number of times set as the number of empty transmissions before release to the eNB, it clears the set SPS resource. By doing so, when the probability of uplink transmission data generation is low, it is possible to release the SPS resource.

[0411] By doing as above, long-term reservation of SPS resources becomes unnecessary. Thereby, it becomes possible to improve the usage efficiency of PUSCH resources.

[0412] Also, in the method disclosed above, two types of padding transmissions are used, but it is not limited to this, and multiple different padding transmissions may be provided to perform padding transmission. The eNB can change its operation depending on the type of padding transmission.

[0413] For example, the UE varies padding transmission according to the downlink reception quality. Two thresholds for the downlink reception quality may be provided to divide it into three reception quality states, and different padding transmissions may be performed according to the three reception quality states. By doing so, the eNB can recognize the degree of the UE's downlink reception quality.

[0414] Also, in order to cause the UE to perform padding transmission, even when there is no uplink scheduling request from the UE, the eNB may schedule UL resources and notify the UE of an uplink grant. Since there is no uplink transmission data, the UE will perform padding transmission using the uplink resources allocated by the uplink grant. This padding transmission may be different padding transmissions according to the aforementioned reception quality states. By doing so, the eNB can recognize the UE's downlink reception quality in a timely and dynamic manner. By doing the above, the eNB can perform diverse and flexible control on the UE.

[0415] Embodiment 6. When a UL split bearer is set for a predetermined bearer, an uplink SPS is set in the 2nd-eNB according to the occurrence status of the data of the bearer.

[0416] When uplink transmission data occurs at the timing of the uplink SPS set on the 2nd-eNB side, not only is uplink transmission performed using the SPS resources for the 2nd-eNB, but also depending on the bearer setting conditions, uplink transmission is also performed for the 1st-eNB at the timing of the SPS.

[0417] If the uplink SPS is not set for the 1st-eNB at the timing of the SPS, the 1st-eNB has to start from transmitting an SR signal.

[0418] Although the 1st-eNB can also be used in the uplink transmission, there is a delay with respect to the 1st-eNB, causing an increase in the transmission delay time. In the present embodiment, a method for solving such a problem is disclosed.

[0419] Perform the same SPS setting for the 1st-eNB as the SPS setting performed for the 2nd-eNB. When a UL split bearer is set, the SPS setting may be performed for the 1st-eNB.

[0420] Disclose a method for setting SPS. Perform the same setting for the SPS for the 1st-eNB as the SPS setting for the 2nd-eNB. It is preferable to enable multiple SPS settings for each eNB.

[0421] The parameters to be set the same do not have to be all parameters. As the parameters to be set the same, there is an SPS interval. As the parameters to be set differently, there is an SPS C-RNTI. The number of UL pre-release empty transmissions may be the same or may be set differently.

[0422] When the SPS is set in the 1st-eNB and the SPS is set in the 2nd-eNB, the 1st-eNB may perform the same setting as the SPS setting for the 2nd-eNB in addition to the SPS setting already set. When the SPS setting already set in the 1st-eNB and the SPS setting for the 2nd-eNB are the same, for example, when the SPS timing is the same, it may be set repeatedly.

[0423] Alternatively, when the SPS setting already set in the 1st-eNB and the SPS setting for the 2nd-eNB are the same, for example, when the SPS timing is the same, instead of setting repeatedly, perform an SPS setting that combines the SPS setting already set in the 1st-eNB and the SPS setting for the 2nd-eNB.

[0424] By doing so, when SPS has already been configured in the 1st-eNB, it becomes possible to configure the 1st-eNB with the same settings as the SPS configuration for the 2nd-eNB without interrupting the existing SPS configuration.

[0425] Disclosed is a method for notifying and configuring the SPS settings to the UE. The 2nd-eNB notifies the UE of the SPS configuration for the 2nd-eNB. Further, the 2nd-eNB notifies the 1st-eNB of the SPS configuration for the 2nd-eNB. It is preferable to use X2 signaling for this notification. Alternatively, it may be performed using S1 signaling via the MME. Thereby, the 1st-eNB can recognize the SPS configuration of the 2nd-eNB. The 1st-eNB applies the parameters for the same settings as the SPS configuration of the 2nd-eNB to the SPS configuration of its own eNB. Examples of the parameters for the same settings include the SPS interval. The number of UL pre-release empty transmissions may be the same or different. The C-RNTI for SPS is independently configured by the eNB itself. The 1st-eNB notifies the UE of these SPS configurations.

[0426] By doing so, the 1st-eNB can configure the UE with the same SPS settings as the 2nd-eNB.

[0427] Disclosed is another SPS configuration method. The same settings as the SPS configuration for the 2nd-eNB are applied to the SPS for the 1st-eNB. It is preferable to enable multiple SPS configurations for each eNB.

[0428] The parameters for the same settings are all the parameters. The SPS interval, the C-RNTI for SPS, and the number of UL pre-release empty transmissions are set to be the same.

[0429] Disclosed is a method for notifying and configuring the SPS settings to the UE. The 2nd-eNB notifies the UE of the SPS settings for the 2nd-eNB. Further, the 2nd-eNB notifies the 1st-eNB of the SPS settings for the 2nd-eNB. It is preferable to use X2 signaling for this notification. Alternatively, it may be performed using S1 signaling via the MME. Thereby, the 1st-eNB can recognize the SPS settings of the 2nd-eNB. The UE applies the SPS settings for the 2nd-eNB to the SPS settings for the 1st-eNB.

[0430] By doing so, the 1st-eNB can configure the same SPS settings as the 2nd-eNB for the UE.

[0431] Also, by doing so, there is no need to notify the UE of the SPS settings from the 1st-eNB. Therefore, it is possible to reduce the amount of signaling on the air interface.

[0432] Disclosed is a method for using the same SPS C-RNTI for the 2nd-eNB and the 1st-eNB. Coordinate in advance between the 2nd-eNB and the 1st-eNB to set the same value. For example, when the 2nd-eNB configures the SPS, notify the SPS C-RNTI to be used to the 1st-eNB in advance.

[0433] If the 1st-eNB can use the notified SPS C-RNTI, it notifies the 2nd-eNB of an Ack. Thereby, the 1st-eNB and the 2nd-eNB can use the same SPS C-RNTI.

[0434] If the 1st-eNB cannot use the notified SPS C-RNTI, it notifies the 2nd-eNB of a Nack. In this case, the 2nd-eNB selects another SPS C-RNTI value again and notifies the 1st-eNB. This is repeated until an Ack is received from the 1st-eNB. By performing such a method, it becomes possible for the 2nd-eNB and the 1st-eNB to use the same SPS C-RNTI.

[0435] For the notification of this information between the 2nd-eNB and the 1st-eNB, it is advisable to use X2 signaling. Alternatively, it may be performed using S1 signaling via the MME.

[0436] The timing of SPS activation determines the start timing of SPS. Therefore, a method for aligning the SPS activation timing in both eNBs is required.

[0437] When the 2nd-eNB decides to notify the UE of SPS activation, it notifies the 1st-eNB of the timing for notifying the UE of SPS activation. Alternatively, it notifies the 1st-eNB of the timing when it notified the UE of SPS activation.

[0438] The timing information may be at least one of the radio frame number and the subframe number.

[0439] The 1st-eNB uses the received timing information to derive the timing when the SPS setting of the 2nd-eNB is activated for the UE, and notifies the UE of SPS activation so as to match that timing.

[0440] If the timing when the 2nd-eNB notifies the UE of SPS activation is not in time, it may notify the UE according to the timing after the subsequent SPS interval. It should be notified as soon as possible.

[0441] By doing so, it is possible to align the SPS activation timings at both eNBs, and the timings of SPS for both eNBs can be made to match.

[0442] For the notification of this information between the 2nd-eNB and the 1st-eNB, X2 signaling may be used. Alternatively, it may be performed using S1 signaling via the MME.

[0443] FIG. 21 is a diagram for explaining a method of performing the same SPS setting as the SPS setting performed for the 2nd-eNB for the 1st-eNB. The 1st-eNB is taken as the MeNB, and the 2nd-eNB is taken as the SeNB.

[0444] In FIG. 21, the DRAT threshold is indicated by reference numeral "1901".

[0445] The SeNB determines the SPS setting. In step ST1902, the SeNB notifies the UE, by RRC individual signaling, of the SPS interval, the number of pre-release empty transmissions, and the SPS C-RNTI.

[0446] Also, in step ST1903, the SeNB notifies the MeNB of the set SPS configuration. The set SPS configuration may be notified by X2 signaling. As the SPS configuration to be notified, the SPS interval may be used. Also, the number of pre-release empty transmissions may also be notified.

[0447] The MeNB sets the same value as the received SeNB configuration as the SPS configuration for the MeNB. The SPS C-RNTI is selected by the MeNB without using the same value as the SeNB.

[0448] In step ST1904, the MeNB notifies the UE, by RRC individual signaling, of the SPS configuration for the MeNB and the SPS C-RNTI.

[0449] The UE detects the PDCCH using the SPS C-RNTIs notified from the SeNB and the MeNB.

[0450] In step ST1905, the SeNB notifies the MeNB of the timing of SPS activation. The MeNB that has received the timing of SPS activation can recognize the timing at which the SeNB activates the SPS.

[0451] In steps ST1906 and ST1907, the SeNB and the MeNB each send an SPS activation to the UE at the activation timing determined by the SeNB. As a result, both the SeNB and the MeNB can set the same SPS activation timing for the UE.

[0452] The order of the notification of the SPS activation timing from the SeNB to the MeNB in step ST1905 and the notification of the SPS activation timing from the SeNB to the UE in step ST1906 may be reversed.

[0453] The SeNB notifies the MeNB of the timing at which it notified the UE of the SPS activation. As a result, it becomes possible to notify the MeNB of the timing at which the SeNB actually performed the SPS activation. By notifying the actual SPS activation timing, it is possible to reduce the occurrence of malfunction such that the SPS activation timings of the SeNB and the MeNB deviate.

[0454] The scheduling of the SPS resources from the MeNB and the scheduling of the SPS resources from the SeNB may be different. The MeNB and the SeNB may each perform scheduling individually.

[0455] Upon receiving the SPS activation, the UE recognizes that the SPS has been activated for both the SeNB and the MeNB.

[0456] In step ST1908 and step ST1909, the UE transmits uplink data to the SeNB and the MeNB at the configured SPS timing.

[0457] In step ST1910, if the amount of uplink transmission data of the UE is less than the DRAT threshold at the configured SPS timing, the UE performs padding transmission to the SeNB and transmits uplink data to the MeNB.

[0458] If padding transmission to the SeNB is continuously performed for the number of times set as the number of pre-release empty transmission times, in step ST1911, the eNB releases the SPS resources configured for the SeNB, and the UE also clears the SPS resources configured for the SeNB.

[0459] Since uplink data is being transmitted to the MeNB, in step ST1911, the SPS resources configured for the MeNB are not released. If there is uplink transmission data, uplink data is transmitted.

[0460] Disclose the release of SPS resources. The eNB where implicit release has occurred may notify other eNBs of this. For example, when implicit release occurs for the configured SPS at the 2nd - eNB, the 2nd - eNB notifies the 1st - eNB that implicit release has occurred. Alternatively, it may notify that the SPS resources have been released or the SPS configuration has been invalidated due to implicit release.

[0461] Upon receiving the release of the SPS resources of the 2nd-eNB, the 1st-eNB may invalidate the same SPS configuration as that set in the 1st-eNB for the 2nd-eNB. Additionally, as appropriate, the 1st-eNB may notify the UE to invalidate the same SPS configuration as that set in the 1st-eNB for the 2nd-eNB. By receiving this notification, the UE can invalidate the same SPS configuration as that set in the 1st-eNB for the 2nd-eNB.

[0462] By doing so, the 1st-eNB can invalidate the same SPS configuration as that of the 2nd-eNB.

[0463] Furthermore, the eNB that notifies the UE of the information indicating the invalidation of the uplink SPS configuration disclosed in the second modification example of Embodiment 4 may notify other eNBs to that effect. Alternatively, the eNB that notifies the UE of the information indicating the invalidation of the uplink SPS configuration may notify other eNBs to that effect in advance.

[0464] For example, when the 2nd-eNB notifies the UE of the information indicating the invalidation of the uplink SPS configuration, it notifies the 1st-eNB that it has notified the UE of the information indicating the invalidation of the uplink SPS configuration.

[0465] Alternatively, when the 2nd-eNB notifies the UE of the information indicating the invalidation of the uplink SPS configuration, it notifies the 1st-eNB that it will notify the UE of the information indicating the invalidation of the uplink SPS configuration. In this case, the timing of invalidating the uplink SPS configuration or the timing of notifying the UE of the information indicating the invalidation of the uplink SPS configuration may be notified to the 1st-eNB.

[0466] Upon receiving information indicating that the 2nd-eNB invalidates the aforementioned uplink SPS configuration, the 1st-eNB may invalidate the same SPS configuration as that of the 2nd-eNB set in the 1st-eNB using the information indicating that the uplink SPS configuration is to be invalidated. Alternatively, the 1st-eNB may determine not to invalidate the same SPS configuration as that of the 2nd-eNB set in the 1st-eNB. Alternatively, the 1st-eNB may modify the same SPS configuration as that of the 2nd-eNB set in the 1st-eNB. For example, it may be reverted to the SPS configuration previously set for the 1st-eNB. The 1st-eNB can flexibly change the SPS configuration set in its own eNB in consideration of the load situation and the like.

[0467] Also, as appropriate, the 1st-eNB may notify the UE to invalidate the same SPS configuration as that of the 2nd-eNB set in the 1st-eNB. By receiving the notification, the UE can invalidate the same SPS configuration as that of the 2nd-eNB set in the 1st-eNB.

[0468] If the 1st-eNB fails to notify the UE of the information indicating that the 2nd-eNB invalidates the uplink SPS configuration in time, the 1st-eNB may notify the UE at the timing after the next SPS interval. Alternatively, the 1st-eNB may notify the UE without waiting for the timing after the next SPS interval. Alternatively, the 1st-eNB may notify the UE immediately.

[0469] By doing so, the 1st-eNB can invalidate the same SPS configuration as that of the 2nd-eNB.

[0470] It has been described that at the timing of the SPS set for the 2nd-eNB, uplink data may be transmitted not only for the 2nd-eNB but also for the 1st-eNB.

[0471] By using the method disclosed in this embodiment, at the timing of the SPS set for the 2nd-eNB, the SPS will be set for the 1st-eNB. Therefore, the UE can transmit uplink data without transmitting an uplink scheduling request at the SPS timing not only to the 2nd-eNB but also to the 1st-eNB. As a result, the transmission delay time for the 1st-eNB can be reduced.

[0472] Embodiment 7. In the UL split bearer, when the data volume of the uplink transmission data is equal to or less than the DRAT threshold, the UE does not transmit the uplink data to the 2nd-eNB.

[0473] Performing padding transmission despite the absence of uplink data transmission to the 2nd-eNB is a waste of the UE's power consumption.

[0474] In particular, even if padding transmissions occur continuously a predetermined number of times and implicit release is not performed, it is not possible to determine implicit release based on the number of padding transmissions, so performing padding transmissions is a waste.

[0475] To solve such a problem, it is advisable not to perform padding transmission when implicit release is not performed.

[0476] The UE does not perform padding transmission when there is no uplink data transmission to the 2nd-eNB at the set SPS timing and implicit release is not performed.

[0477] FIG. 22 is a diagram for explaining a method of not performing padding transmission when implicit release is not performed. Let the 1st-eNB be the MeNB and the 2nd-eNB be the SeNB. It shows the case where SPS is set for both the MeNB and the SeNB. Since FIG. 22 is similar to FIG. 15, mainly the different parts will be described.

[0478] In step ST1008, the SeNB notifies the UE, using PDCCH, of the activation with an uplink grant for uplink SPS. The activation includes information indicating that the setting of the uplink SPS is not to be invalidated. Thereby, the UE can recognize that it does not perform implicit release and does not invalidate the setting of the uplink SPS.

[0479] The UE that has received the activation of SPS from the SeNB executes SPS with the set resources, does not perform implicit release, and does not invalidate the setting of the uplink SPS. Even if uplink transmission data does not occur the predetermined number of times in advance for the UE with respect to the SeNB, both the eNB and the UE are set not to perform implicit release and not to invalidate the setting of the uplink SPS.

[0480] In step ST1301, consider the case where uplink data with a data volume smaller than the DRAT threshold occurs in the UE at the timing of SPS set for the SeNB.

[0481] In this case, in step ST1301, the UE transmits the uplink data to the MeNB. No uplink transmission data occurs for the SeNB.

[0482] When implicit release is not performed and no uplink transmission data occurs, padding transmission is not performed. Therefore, in step ST2001, the UE does not perform padding transmission for the SeNB.

[0483] From step ST2001 to step ST2002, when uplink data with a data volume smaller than the DRAT threshold occurs in the UE at the timing of SPS set for the SeNB, similarly, from step ST1301 to step ST1302, the UE transmits the uplink data to the MeNB, but does not perform padding transmission for the SeNB.

[0484] If there is no uplink transmission data generated continuously for the number of times set as the pre-release empty transmission count for the serving eNB (SeNB), the UE does not perform padding transmission using that SPS resource. In such a case, the UE does not perform implicit release received in step ST1008. The UE does not clear the SPS resource in step ST1204 according to the setting that does not invalidate the uplink SPS setting. The eNB also does not release the SPS resource. In step ST1204, implicit release is not performed and the SPS resource is not released.

[0485] In step ST1204, if uplink data with a data volume equal to or greater than the DRAT threshold is generated at the UE at the SPS timing set for the serving eNB (SeNB), in step ST1401, the UE can perform uplink data transmission using the set SPS resource to the SeNB.

[0486] By doing so, when implicit release is not performed, it is possible not to perform padding transmission when there is no uplink transmission data to the serving eNB (SeNB). Since the UE does not perform padding transmission, it is possible to reduce the power consumption of the UE. Also, by not performing padding transmission when there is no uplink transmission data to the serving eNB (SeNB), it is possible to reduce interference in the uplink.

[0487] When implicit release is performed, padding transmission may be performed. As the method of performing implicit release, the methods disclosed in Embodiment 4, Modification Example 1 of Embodiment 4, and Modification Example 2 of Embodiment 4 may be applied. The eNB may notify the UE of information indicating to start padding transmission together with the notification of the start of implicit release.

[0488] By doing so, when implicit release is not performed and uplink transmission data does not occur for the 2nd - eNB, it becomes possible not to perform padding transmission. Also, when implicit release is performed, when uplink transmission data does not occur for the 2nd - eNB, it becomes possible to perform padding transmission.

[0489] This enables the normal operation of implicit release and also enables the reduction of the power consumption of the UE.

[0490] When implicit release is not performed, when uplink transmission data does not occur for the 2nd - eNB, as specific examples of the method of setting not to perform padding transmission, the following two cases (1) and (2) are disclosed.

[0491] (1) Decide statically in advance by a standard or the like.

[0492] (2) Provide information indicating not to perform padding transmission and notify the UE from the eNB.

[0493] In the method of the above - mentioned (1), when implicit release is not performed, when uplink transmission data does not occur for the 2nd - eNB, it is statically determined not to perform padding transmission. By determining this in advance by a standard or the like, it becomes possible for the eNB and the UE to recognize it, so that consistent operation is possible and malfunctions can be reduced.

[0494] In the method of the above - mentioned (2), by notifying the UE from the eNB of the information indicating not to perform padding transmission, when uplink transmission data does not occur for the 2nd - eNB, it becomes possible to dynamically set not to perform padding transmission. The eNB may notify the UE of the information when implicit release is not performed at the 2nd - eNB. When the UE receives the information indicating not to perform padding transmission, when uplink data does not occur for the 2nd - eNB, it does not perform padding transmission.

[0495] Information indicating not to perform the padding transmission in (2) above may be notified from the eNB to the UE. The eNB may be the 1st-eNB or the 2nd-eNB. For example, when notifying the UE from the 2nd-eNB, it may be directly notified from the 2nd-eNB to the UE, or may be notified from the 2nd-eNB to the UE via the 1st-eNB. For the notification of information between eNBs, X2 signaling may be used. Alternatively, S1 signaling may be used via the MME.

[0496] As specific examples of the signaling method for notifying the UE from the eNB of the information indicating not to perform the padding transmission, the following three cases (1) to (3) are disclosed.

[0497] (1) RRC signaling. For example, it may be notified included in the signaling for the configuration of the SPS.

[0498] (2) MAC signaling. For example, a MAC CE including the information indicating not to perform the padding transmission may be provided and notified by MAC signaling.

[0499] (3) L1 / L2 signaling. For example, PDCCH or EPDCCH. For example, it may be notified included in the SPS activation.

[0500] Although it has been disclosed to provide the information indicating not to perform the padding transmission and notify it from the eNB to the UE, the information indicating to perform the padding transmission may be provided. The information indicating to perform the padding transmission may be notified from the eNB to the UE. Thereby, when implicit release is not performed and uplink transmission data does not occur for the 2nd-eNB, it becomes possible to dynamically set the presence or absence of the padding transmission, and flexible operation becomes possible according to the communication status and load status of the 2nd-eNB.

[0501] Embodiment 8. In Embodiment 7, a method of not performing padding transmission when there is no uplink transmission data at the set SPS timing was disclosed.

[0502] If padding transmission is not performed, the eNB cannot identify whether it could not receive even though actual uplink data was transmitted, or whether it could not receive because there was no padding transmission. In this embodiment, a method for solving such a problem is disclosed.

[0503] Even when it is set not to perform padding transmission, HARQ is operated. The eNB operates HARQ when it is set not to perform padding transmission. The UE performs HARQ when there is uplink transmission data, and does not perform padding transmission or retransmission when there is no uplink transmission data.

[0504] Conventionally, padding transmission performed when there is no uplink transmission data at the set SPS timing is subject to HARQ. The eNB can determine whether uplink transmission data has been sent by receiving the padding transmission. Therefore, even when there is no uplink transmission data at the set SPS timing, the UE performs padding transmission, and when it receives a Nack, which is a reception unsuccessful signal, from the eNB, it retransmits the padding transmission.

[0505] In the method disclosed in this embodiment, the eNB operates HARQ, but the UE does not perform padding transmission when there is no uplink transmission data at the set SPS timing, and does not retransmit the padding transmission even if it receives a Nack, which is a reception unsuccessful signal, from the eNB, which is different from the conventional method.

[0506] Even if the UE receives a Nack from the eNB when it does not perform padding transmission, it will not perform retransmission of padding transmission. Therefore, since there is no retransmission from the UE, the eNB fails to receive, and sends a Nack again. The UE will receive the Nack again from the eNB. Also for this Nack, the UE will not perform retransmission of padding transmission. Since the UE does not perform padding transmission nor retransmission of padding transmission, such an operation will be repeated. Therefore, the eNB will continue to send Nacks to the UE. A method for solving such a problem is disclosed.

[0507] The eNB may set the maximum number of retransmissions. For HARQ when the initial transmission is performed using the uplink SPS resource, the maximum number of retransmissions may be set.

[0508] When the reception failure continues, if the eNB sends Nacks the maximum number of retransmissions but still fails to receive, the HARQ is stopped.

[0509] The maximum number of retransmissions may be statically determined in advance by a standard or the like. Alternatively, the eNB may determine it. This enables dynamic change according to the communication situation and the load situation. Alternatively, the OAM (operation administration and maintenance) may determine it. This enables determination considering the situations of a plurality of eNBs. Alternatively, the operator may determine it. It may be determined as one of the system design parameters.

[0510] The maximum number of retransmissions disclosed in this embodiment may be set differently from the maximum number of retransmissions set in the conventional HARQ. For example, the maximum number of retransmissions disclosed in this embodiment may be made smaller than the maximum number of retransmissions set in the conventional HARQ. By making the maximum number of retransmissions disclosed in this embodiment smaller, it is possible to reduce the number of Nacks sent from the eNB to the UE when there is no uplink transmission data and no padding transmission. This makes it possible to reduce the waste of radio resources for Nacks.

[0511] FIG. 23 is a diagram for explaining a HARQ method when padding transmission is not performed. Let the 1st - eNB be the MeNB and the 2nd - eNB be the SeNB. FIG. 23 shows the case where SPS is set in the SeNB. It shows the case where padding transmission is not performed when implicit release is not performed and no uplink transmission data is generated. In step ST2108, the SeNB notifies the UE of activation using the PDCCH with an uplink grant of the uplink SPS. The activation includes information indicating that the setting of the uplink SPS is not invalidated. Thus, the UE can recognize that padding transmission is not performed when implicit release is not performed and no uplink transmission data is generated.

[0512] In step ST2101, consider the case where uplink data with a data volume equal to or greater than the DRAT threshold is generated in the UE at the timing of the SPS set for the SeNB. In this case, in step ST2101, the UE transmits uplink data to the SeNB using the SPS resource set for the SeNB. Assume that the eNB receives the uplink data from the UE and the reception is successful. In this case, in step ST2102, the SeNB transmits an Ack, which is a reception success signal, to the UE. When the UE receives the Ack, it determines that the uplink data has been received by the SeNB and does not perform re - transmission.

[0513] Next, in ST2103, the UE transmits uplink data to the SeNB at the timing of the set SPS. Assume that the SeNB receives the uplink data from the UE and the reception is unsuccessful. In this case, in step ST2104, the SeNB transmits a Nack to the UE.

[0514] When the UE receives the Nack, it determines that the uplink data has not been received by the SeNB and, in step ST2105, re - transmits the uplink data to the SeNB. Thus, when the UE transmits uplink data to the SeNB and receives a Nack from the SeNB, it re - transmits the uplink data.

[0515] In step ST2105, assume that the SeNB receives the retransmission of the uplink data from the UE and the reception is successful. In this case, in step ST2109, the SeNB transmits an Ack to the UE.

[0516] When the UE receives the Ack, it determines that the uplink retransmission data has been received by the eNB and does not perform retransmission.

[0517] Next, consider the case where in step ST2106, uplink data with a data volume smaller than the DRAT threshold is generated at the UE at the timing of the SPS set for the SeNB. In this case, in step ST2110, the UE transmits the uplink data to the MeNB, but does not transmit the uplink data using the SPS resources set for the SeNB. In step ST2108, when no uplink transmission data is generated, since it is set not to perform padding transmission, the UE also does not perform padding transmission.

[0518] In step ST2106, since the SeNB does not receive padding transmission from the UE, the reception is unsuccessful. In this case, in step ST2111, the SeNB transmits a Nack to the UE.

[0519] The UE may or may not receive the Nack. Even if the UE receives the Nack, it does not perform retransmission. Also, the UE does not perform padding transmission.

[0520] In step ST2107, since nothing is transmitted from the UE to the SeNB, the reception is unsuccessful. In this case, in step ST2112, the SeNB transmits a Nack to the UE again.

[0521] Similarly, the UE may or may not receive the Nack. Even if the UE receives the Nack, it does not perform retransmission. Also, the UE does not perform padding transmission.

[0522] When the number of Nack transmissions reaches the maximum number of transmissions, the eNB stops HARQ. If the maximum number of retransmissions is not set, the Nack transmission will be repeated. However, in this embodiment, since the maximum number of retransmissions is set, it is possible to stop HARQ.

[0523] By using the method disclosed in this embodiment, when uplink data is transmitted from the UE, HARQ will operate, improving the reception performance of the uplink data.

[0524] Also, when there is no uplink transmission data, even if a Nack is transmitted from the eNB, the UE will not retransmit and will not perform padding transmission either. The UE only needs to retransmit according to the Nack from the eNB when uplink data transmission is performed. Therefore, since the UE's transmission is limited to the case when uplink data is transmitted, it is possible to reduce the increase in power consumption.

[0525] Embodiment 8 Variation 1. In this variation, another method for solving the problems shown in Embodiment 8 is disclosed. The 2nd-eNB determines whether data has been generated for the 2nd-eNB. The 2nd-eNB determines whether to operate HARQ using the result.

[0526] A method for determining whether data has been generated for the 2nd-eNB is disclosed. The 2nd-eNB notifies the 1st-eNB of the SPS settings of its own eNB in advance. The SPS settings may be the SPS timing. Alternatively, it may be the timing when the SPS interval and SPS activation were notified to the UE.

[0527] This enables the 1st-eNB to recognize the SPS timing set by the 2nd-eNB.

[0528] The 1st eNB determines whether the data volume of the uplink transmission data generated from the UE is smaller than the DRAT threshold at the timing of the SPS of the 2nd eNB. The 1st eNB notifies the 2nd eNB of the determination result. The 2nd eNB determines whether data has been generated for itself based on the determination result received from the 1st eNB.

[0529] When the determination result notified by the 1st eNB to the 2nd eNB is smaller than the DRAT threshold, the 2nd eNB determines that no data has been generated for itself.

[0530] When the determination result notified by the 1st eNB to the 2nd eNB is equal to or greater than the DRAT threshold, the 2nd eNB determines that data has been generated for itself.

[0531] Disclosed is a method for the 2nd eNB to determine whether to operate HARQ. When the 2nd eNB determines that data has been generated for itself, it operates HARQ.

[0532] When the 2nd eNB determines that no data has been generated for itself, it stops HARQ.

[0533] In such a method, it is necessary to notify information from the 1st eNB to the 2nd eNB. In this case, since communication is performed via a backhaul such as the X2 interface or the S1 interface, there may be a case where the HARQ performed by the 2nd eNB cannot be immediately responded to in terms of time.

[0534] However, even if it is not possible to immediately respond to HARQ, it will be possible to respond after a delay due to backhaul communication or the like. Therefore, it is possible to prevent HARQ from continuing indefinitely. As a result, it is possible to improve the resource utilization efficiency of the 2nd eNB.

[0535] Even though the data transmitted to the 1st-eNB is smaller than the DRAT threshold, data may still be transmitted to the 2nd-eNB. For example, when the scheduling ratio between the 1st-eNB and the 2nd-eNB when the DRAT threshold is exceeded is set to 1:2. In this case, the amount of data transmitted to the 1st-eNB is 1 / 3. In such a case, it may be smaller than the DRAT threshold.

[0536] In such a case, HARQ will not be performed on the 2nd-eNB side. Even though data is transmitted to the 2nd-eNB, HARQ is not performed, which becomes a problem. A method for solving such a problem is disclosed.

[0537] The 1st-eNB acquires the scheduling ratio between the 1st-eNB and the 2nd-eNB. For example, when the 2nd-eNB determines the scheduling ratio, it may be advisable to notify the 1st-eNB of the scheduling ratio from the 2nd-eNB in advance. When the 1st-eNB determines the scheduling ratio, there is no need to notify.

[0538] The 1st-eNB determines whether it is smaller than the DRAT threshold in consideration of the scheduling ratio.

[0539] By doing so, depending on the scheduling ratio between the 1st-eNB and the 2nd-eNB when the DRAT threshold is exceeded, it is possible to prevent HARQ from not operating when data transmitted to the 1st-eNB is smaller than the DRAT threshold but data is still transmitted to the 2nd-eNB.

[0540] Therefore, when there is uplink transmission data from the UE to the 2nd-eNB, the reception performance of the uplink transmission data can be improved.

[0541] Also, since HARQ can be stopped, it becomes possible to improve the resource utilization efficiency of the 2nd-eNB.

[0542] Embodiment 8, Variation 2. Disclose another method for solving the problems shown in Embodiment 8. The 2nd-eNB measures the uplink power of the SPS resources configured for the 2nd-eNB. The 2nd-eNB may measure the uplink communication quality.

[0543] The 2nd-eNB may measure, as the uplink power, the received signal strength (RSSI), or the interference over thermal noise (IOT), the reference signal received power (RSRP), the signal to interference plus noise power ratio (SINR), etc. Alternatively, the 2nd-eNB may measure the received power of the reference signal of the physical uplink shared channel (PUSCH) used for the configured SPS resources.

[0544] The 2nd-eNB may measure the reference signal received quality (RSRQ) as the uplink communication quality. Alternatively, the 2nd-eNB may measure the received quality of the reference signal of the PUSCH.

[0545] When the uplink power or the uplink communication quality of the SPS resources configured for the 2nd-eNB is higher than a predetermined threshold, the 2nd-eNB determines that uplink data has been transmitted to the 2nd-eNB.

[0546] When the uplink power or the uplink communication quality of the SPS resources configured for the 2nd-eNB is lower than a predetermined threshold, the 2nd-eNB determines that uplink data has not been transmitted to the 2nd-eNB.

[0547] Disclose a method for the 2nd-eNB to determine whether to operate hybrid automatic repeat request (HARQ). When the 2nd-eNB determines that data has been transmitted to the 2nd-eNB itself, the 2nd-eNB operates HARQ. When the 2nd-eNB determines that data has not been transmitted to the 2nd-eNB itself, the 2nd-eNB stops HARQ.

[0548] Since it requires measurement, it may not be able to immediately respond to HARQ performed at the 2nd-eNB in terms of time. However, even if it cannot immediately respond to HARQ, it will be able to respond after a delay due to measurement or the like. Therefore, it is possible to prevent HARQ from continuing indefinitely. As a result, it becomes possible to improve the resource utilization efficiency of the 2nd-eNB.

[0549] Also, signaling between eNBs becomes unnecessary, and it becomes possible to suppress an increase in the amount of signaling.

[0550] Embodiment 9. When the data volume of the uplink transmission data is equal to or less than the DRAT threshold, the UE does not transmit uplink data to the 2nd-eNB. Performing padding transmission despite the absence of uplink data transmission to the 2nd-eNB is a waste of the UE's power consumption.

[0551] However, when implicit release is operating, if padding transmission is not performed, implicit release is not performed, and the release of the configured SPS resources is not performed. If the SPS resources are not released, the resources cannot be used by other UEs, and the utilization efficiency of the PUSCH resources is reduced. In this embodiment, a method for solving such problems is disclosed.

[0552] Change the frequency of padding transmission when there is no uplink transmission data. Specifically, thinning out the padding transmission.

[0553] In the method of padding transmission disclosed above, when the data volume of the uplink transmission data is equal to or less than the DRAT threshold, padding transmission is always performed to the 2nd-eNB. On the other hand, in the method disclosed in this embodiment, when the data volume of the uplink transmission data is equal to or less than the DRAT threshold, the padding transmission to be transmitted to the 2nd-eNB is thinned out.

[0554] For example, the case where padding transmission is decimated once every two times is shown. At the execution timing of the first padding transmission, the UE does not perform padding transmission. The UE performs padding transmission at the execution timing of the second padding transmission.

[0555] In this way, the number of times of performing padding transmission per several times, that is, the frequency of performing padding transmission, may be referred to as "padding transmission frequency". In the above example, the padding transmission frequency is "2".

[0556] The padding transmission frequency may be statically determined in advance by a standard or the like, or may be changed semi-statically or dynamically. The padding transmission frequency may be set by the eNB and notified from the eNB to the UE. When notified from the eNB to the UE, it may be included in the message of the SPS setting or may be included in the SPS activation.

[0557] FIG. 24 is a diagram for explaining an implicit release method when padding transmission is decimated. Let the 1st-eNB be the MeNB and the 2nd-eNB be the SeNB. The case where SPS is set in the SeNB is shown. The case where the padding transmission frequency is "2" is shown. Let the number of pre-release empty transmissions for implicit release be "3". Assume that the SPS setting for the SeNB has already been performed.

[0558] In step ST2209, the SeNB notifies the UE of activation using the PDCCH with an uplink grant for uplink SPS. The activation includes information on the padding transmission frequency. Thereby, the UE can recognize the number of times of decimating the padding transmission.

[0559] In step ST2201, consider the case where uplink data with a data amount equal to or greater than the DRAT threshold occurs in the UE at the timing of the SPS set for the SeNB. In this case, in step ST2201, the UE transmits uplink data to the SeNB using the SPS resource set for the SeNB.

[0560] In step ST2202, when uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS set for the SeNB, the UE determines that the padding transmission timing for the SeNB is the first time and does not perform padding transmission.

[0561] In step ST2203, when uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS set for the SeNB, the UE determines that the padding transmission timing for the SeNB is the second time. Since the padding transmission frequency is "2", the UE performs padding transmission.

[0562] When the UE performs padding transmission to the SeNB, it resets the count of the padding transmission timing.

[0563] After the UE resets the count of the padding transmission timing, in step ST2204, when uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS set for the SeNB, the UE determines that the padding transmission timing for the SeNB is the first time and does not perform padding transmission.

[0564] In step ST2205, when uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS set for the SeNB, the UE determines that the padding transmission timing for the SeNB is the second time. Since the padding transmission frequency is "2", the UE performs padding transmission.

[0565] When the UE performs padding transmission to the SeNB, it resets the count of the padding transmission timing.

[0566] Similarly, in step ST2206, the UE does not perform padding transmission to the SeNB. In step ST2207, the UE performs padding transmission to the SeNB. Then, the UE resets the count of the padding transmission timing.

[0567] In step ST2203, the SeNB receives the first padding transmission from the UE. Also, in step ST2205, the SeNB receives the second padding transmission from the UE, and in step ST2207, the SeNB receives the third padding transmission from the UE.

[0568] From step ST2203 to step ST2207, while the SeNB is receiving the padding transmission from the UE, it does not receive uplink data. Since the padding transmission is received for the number of pre-release empty transmission times, here three times in a row, an implicit release is performed. Then, in step ST2208, the SeNB releases the configured SPS resource. When the SeNB receives the padding transmission for the number of pre-release empty transmission times, here three times in a row, in step ST2208, the UE clears the SPS configuration.

[0569] By doing so, it becomes possible to reduce the padding transmission when there is no uplink transmission data at the timing of the SPS set for the SeNB. By reducing the padding transmission, it becomes possible to reduce the power consumption of the UE.

[0570] Also, since the padding transmission is executed, it becomes possible to operate the implicit release. Therefore, it becomes possible to suppress a reduction in the usage efficiency of the PUSCH resource.

[0571] In the example shown in FIG. 24, when the UE performs the padding transmission, it resets the count of the padding transmission timing. As another method, the UE may reset the count of the padding transmission timing when performing the padding transmission and when performing the uplink data transmission. Since the count of the padding transmission timing is also reset when performing the uplink data transmission, it becomes possible to further reduce the number of padding transmissions.

[0572] The method for resetting the count of padding transmission timing may be statically determined in advance by a standard or the like, or may be notified from the eNB to the UE. This notification may be included in the SPS setting message or in the SPS activation. It may also be notified together with the padding transmission frequency.

[0573] FIG. 25 is a diagram showing another example of the implicit release method when thinning out padding transmission. The 1st-eNB is the MeNB, and the 2nd-eNB is the SeNB. The case where SPS is set in the SeNB is shown.

[0574] Since FIG. 25 is similar to FIG. 24, mainly different parts will be described.

[0575] FIG. 25 shows the case where the padding transmission frequency is "4".

[0576] Instead of the number of pre-release empty transmissions for implicit release, the number of predetermined padding transmission timings for implicit release is provided. As the number of predetermined padding transmission timings for implicit release, a parameter "implicitReleaseAfter_T" is used. In the following description, the number of predetermined padding transmission timings for implicit release may be referred to as the "number of pre-release empty transmission timings". In FIG. 25, the number of pre-release empty transmission timings is set to "8". The UE may reset the count of the padding transmission timing when performing padding transmission and when transmitting uplink data.

[0577] The number of pre-release empty transmission timings may be statically determined in advance by a standard or the like, or may be notified from the eNB to the UE. When notified from the eNB to the UE, it may be included in the SPS setting message or in the SPS activation.

[0578] Assume that the SPS for the SeNB has already been configured. In step ST2310, the SeNB notifies the UE to activate the uplink grant of the uplink SPS using the PDCCH. The activation includes information on the padding transmission frequency and the number of times of the pre-release null transmission timing. As a result, the UE can recognize the number of times to skip padding transmission and the number of times of the predetermined padding transmission timing for implicit release.

[0579] In step ST2311, consider the case where uplink data with a data volume equal to or greater than the DRAT threshold is generated at the UE at the timing of the SPS configured for the SeNB. In this case, in step ST2311, the UE transmits uplink data to the SeNB using the SPS resources configured for the SeNB.

[0580] When the UE transmits uplink data, it resets the count of the padding transmission timing.

[0581] In step ST2301, when uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS configured for the SeNB, the UE determines that the padding transmission timing is the first time and does not perform padding transmission.

[0582] In step ST2302, when uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS configured for the SeNB, the UE determines that the padding transmission timing is the second time and does not perform padding transmission.

[0583] In step ST2303, when uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS configured for the SeNB, the UE determines that the padding transmission timing is the third time and does not perform padding transmission.

[0584] In step ST2304, if uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS set for the SeNB, the UE determines that the padding transmission timing is the fourth time, and since the padding transmission frequency is "4", the UE performs padding transmission.

[0585] When the UE performs padding transmission, the UE resets the count of the padding transmission timing.

[0586] After the UE resets the count of the padding transmission timing, in step ST2305, if uplink data with a data volume smaller than the DRAT threshold is generated at the timing of the SPS set for the SeNB, the UE determines that the padding transmission timing is the first time and does not perform padding transmission.

[0587] Similarly, in steps ST2306 and ST2307, the UE does not perform padding transmission. In step ST2308, the UE performs padding transmission. Then, the UE resets the count of the padding transmission timing.

[0588] In step ST2304, the SeNB receives the first padding transmission from the UE. Since the SeNB has received the padding transmission from the UE once, considering that the padding transmission frequency is "4", the SeNB determines that the padding transmission timing has reached 4 times or more. Since the number of pre-release empty transmission timings has not reached 8 or more, the SeNB maintains the SPS resource and receives from the UE using the SPS resource.

[0589] In step ST2308, the SeNB receives the second padding transmission from the UE. Since the SeNB has received the padding transmission from the UE twice in a row, the SeNB determines that the number of pre-release empty transmission timings has reached 8 or more.

[0590] If the SeNB determines that the number of pre-release empty transmission timings is 8 or more, it performs implicit release and releases the configured SPS resources in step ST2309.

[0591] When the padding transmission timing for the UE is continuous with the number of pre-release empty transmission timings with respect to the SeNB, the UE clears the SPS configuration. Alternatively, since padding transmission has been performed twice in a row, considering that the padding frequency is "4", it is determined that the padding transmission timing is continuous for more than the number of pre-release empty transmission timings, and implicit release is performed, and the configured SPS resources may be cleared.

[0592] Regarding HARQ when padding transmission is not performed, the method disclosed in Embodiment 8 to Modification Example 2 of Embodiment 8 may be applied.

[0593] By using the method disclosed in this embodiment, it is possible to reduce padding transmission when there is no uplink data transmission at the timing of SPS configured for the SeNB. By reducing padding transmission, it is possible to reduce the power consumption of the UE.

[0594] Also, since padding transmission is executed, it is possible to operate implicit release. Therefore, it is possible to suppress a reduction in the usage efficiency of PUSCH resources.

[0595] Also, by making it possible to set the padding transmission frequency, it becomes possible to flexibly respond to requirements such as the desired communication quality, allowable delay amount, or desired continuous operation time of the UE for each UE or bearer for which SPS is configured for the 2nd-eNB.

[0596] Embodiment 10. In Embodiments 1 to 9, when setting the UL split bearer, the problems that occur when SPS is set in the 2nd - eNB were shown, and solutions thereto were disclosed. Originally, it is required to reduce the frequency of occurrence of such problems. In this embodiment, a method for reducing the frequency of occurrence of such problems is disclosed.

[0597] When the data generation cycles are different in a plurality of communications or bearers, set SPS for the communication or bearer in which data is generated in a short cycle in the 1st - eNB.

[0598] It is preferable to set the period of the SPS of the 1st - eNB to be less than or equal to the SPS period of the 2nd - eNB (the period of the SPS of the 1st - eNB ≤ the SPS period of the 2nd - eNB).

[0599] The DRAT threshold may be set to the maximum value of the data amount generated in a short cycle or more. Alternatively, the DRAT threshold may be set to be less than or equal to the minimum value of the data amount generated in a long cycle.

[0600] By doing so, when setting the UL split bearer and setting SPS in the 2nd - eNB, it becomes possible to reduce the number of SPS timing occurrences in the 2nd - eNB. On the other hand, since the 1st - eNB can always transmit uplink data, normal SPS processing is possible. Therefore, the frequency of occurrence of the problems shown in Embodiments 1 to 9 can be reduced.

[0601] It becomes possible to reduce the occurrence of unstable operations and malfunction of the eNB and UE, improve the usage efficiency of radio resources, and reduce the power consumption of the UE.

[0602] When there are data or bearers with multiple different communication capacities and the larger-capacity ones occur in a shorter cycle, the eNB suitable for large-capacity communication may be used as the 1st-eNB. Since the 1st-eNB can always transmit uplink data, setting the eNB suitable for large-capacity communication as the 1st-eNB enables SPS processing suitable for large-capacity communication.

[0603] Embodiment 10, Variation 1. Another method for solving the problems described in Embodiment 10 is disclosed. For one UE, it is preferable to enable one eNB to set multiple SPSs. For example, for one UE, one eNB sets SPS for each bearer. Among the bearers, there are some for which the data generation cycle and data volume for each bearer can be grasped to a certain extent. By setting SPS for each bearer, it becomes possible to set SPS suitable for the data generation cycle and data volume for each bearer.

[0604] Also, the DRAT threshold is set for each bearer. Therefore, by setting SPS for each bearer, it becomes possible to set SPS suitable for the data generation cycle and data volume for each bearer, as well as to set the DRAT threshold. This can reduce the frequency of occurrence of the problems shown in Embodiments 1 to 9. Also, it becomes possible to flexibly respond to requirements such as the desired communication quality and allowable delay amount for each bearer.

[0605] The setting of SPS may be for each bearer group including one or more bearers instead of for each bearer. For example, by grouping bearers with similar data generation cycles and data volumes into the same group, it becomes possible to reduce the number of SPSs set by the eNB for one UE, and it becomes possible to simplify the control.

[0606] Embodiment 10, Variation 2. Another method for solving the problems described in Embodiment 10 is disclosed. The eNB measures the time variation of the data volume of the uplink transmission data from the UE, and uses the measurement result to derive the time variation of the probability that the uplink transmission data occurs. In other words, the eNB predicts the time variation of the probability that the uplink transmission data occurs using the measurement result of the time variation of the data volume of the uplink transmission data.

[0607] Statistical processing may be performed to derive the probability that the uplink transmission data occurs. From the derived time variation of the probability that the uplink transmission data occurs, it is derived at which uplink transmission timing the probability that the uplink transmission data occurs is high.

[0608] The eNB performs SPS setting, SPS resource scheduling, and SPS activation and deactivation according to the derived time variation of the probability that the uplink transmission data occurs. By doing so, the eNB can set the SPS suitable for the time variation of the data volume of the uplink transmission data from the UE.

[0609] Although the derivation of the time variation of the probability that the uplink transmission data occurs has been disclosed, the time variation of the data generation amount may also be derived. Thereby, it becomes possible to derive how much radio resources should be allocated as the SPS resources. Therefore, it becomes possible to accurately perform the scheduling of the SPS resources.

[0610] Although a method has been disclosed in which the eNB measures the time variation of the data volume of the uplink transmission data from the UE and uses the measurement result to derive the time variation of the probability that the uplink transmission data occurs, the UE may measure the time variation of the data generation amount of the uplink transmission data and use the measurement result to derive the time variation of the probability that the uplink transmission data occurs. Statistical processing may be performed to derive the probability that the uplink transmission data occurs. The UE derives at which uplink transmission timing the probability that the uplink transmission data occurs is high from the derived time variation of the probability that the uplink transmission data occurs.

[0611] The UE notifies the eNB of the time variation of the probability that the derived uplink transmission data will occur, or information regarding at which uplink transmission timing the probability that uplink transmission data will occur is high. It is advisable to use RRC signaling for this notification. By using RRC signaling, it becomes possible to notify a large amount of information.

[0612] Notification may also be made using MAC signaling or L1 / L2 control signals. When using MAC signaling or L1 / L2 control signals, the amount of information that can be notified becomes small, but the time required for notification can be shortened. Therefore, the derived value can be reflected with low latency.

[0613] The eNB uses the information notified by the UE regarding the time variation of the probability that the derived uplink transmission data will occur, or information regarding at which uplink transmission timing the probability that uplink transmission data will occur is high, to perform SPS setting, SPS resource scheduling, and SPS activation and deactivation.

[0614] By doing so, since the UE can directly measure the time variation of the uplink transmission data occurring in the UE, it becomes possible to derive the time variation of the probability that uplink transmission data will occur regardless of the radio wave propagation environment.

[0615] The UE may derive SPS setting, SPS resource scheduling, and SPS timing according to the time variation of the probability that the derived uplink transmission data will occur. The UE notifies the eNB of the information regarding the derived SPS setting, SPS resource scheduling, and SPS timing. By doing so, it becomes possible to reduce the amount of information notified from the UE to the eNB.

[0616] The measurement of the temporal change in the data volume of uplink transmission data or the generation amount of uplink transmission data, and the derivation of the temporal change in the probability of the occurrence of uplink transmission data may be performed for each UE or for each bearer. Alternatively, it may be performed for each content or for each application. Thereby, it becomes possible to perform SPS settings suitable for each UE, each bearer, each content, and each application.

[0617] Although the derivation of the temporal change in the probability of the occurrence of uplink transmission data has been disclosed, the temporal change in the generation amount of uplink transmission data may be derived. Alternatively, the temporal change in the uplink throughput may be derived. By using these values, it becomes possible to derive how much radio resources should be allocated as SPS resources. Therefore, it becomes possible to accurately schedule SPS resources.

[0618] By applying the above-described method to the SPS setting of the 2nd-eNB, it becomes possible to reduce the situation where uplink transmission data does not occur in the UE even though SPS resources are allocated in the 2nd-eNB. Further, it may be applied to the SPS setting of the 1st-eNB. Also in the 1st-eNB, appropriate SPS setting becomes possible.

[0619] In the above-described method, the derivation of SPS setting, SPS resource scheduling, and SPS timing in accordance with the temporal change in the probability of the occurrence of uplink transmission data has been disclosed. As another method, it may be applied to the setting of the DRAT threshold. The DRAT threshold is set in accordance with the temporal change in the probability of the occurrence of uplink transmission data.

[0620] For example, the eNB may notify other eNBs that are performing DC of the result of deriving the time change of the probability that uplink transmission data is generated. Also, other eNBs may derive the time change of the probability that uplink transmission data to their own eNB is generated. Other eNBs may use this information to set the threshold of DRAT. Since other eNBs know the time change of the probability that uplink transmission data to each eNB is generated, they can flexibly determine how to set the threshold of DRAT.

[0621] The methods disclosed in Modification Example 1 and Modification Example 2 of Embodiment 10 may be applied to the 1st-eNB. Also, it may be applied as appropriate not only when DC is set. As a result, the same effects as those of Modification Example 1 and Modification Example 2 of Embodiment 10 can be obtained.

[0622] Embodiment 11. In 3GPP, pre-scheduling is being considered as a method for reducing the delay when a UE in a connected state with one cell starts uplink transmission. As methods of pre-scheduling, there are a method using SPS and a method using dynamic scheduling (see Non-Patent Document 10). However, these methods are for the case where the UE is connected to one cell, and there has been no discussion about the pre-scheduling method when dual connectivity (DC) is set.

[0623] As described above, in 3GPP, DC in which the UE connects to two eNBs and communicates has been introduced. DC is an important technology for increasing communication capacity. In this embodiment, a method for setting pre-scheduling when DC is set for the UE is disclosed.

[0624] The eNB that supports pre-scheduling is only the MeNB. The eNB that supports pre-scheduling may be determined statically in advance by a standard or the like.

[0625] If an eNB that supports press scheduling is not determined in advance, for example, if the SeNB independently sets press scheduling for the UE, there may be a situation where the UE does not support press scheduling for the SeNB. In such a case, malfunctions may occur, and there is a possibility that DC cannot be executed. Therefore, by statically determining in advance the eNB that supports press scheduling, the method for setting press scheduling in DC between the UE and the eNB can be clarified, and the occurrence of malfunctions can be reduced.

[0626] In DC, data can be transmitted from both eNBs. Therefore, if only the MeNB supports press scheduling, the reduction in the uplink transmission delay as a bearer is small.

[0627] Therefore, in DC, it is preferable that the SeNB supports press scheduling. In DC, the eNBs that support press scheduling may be the MeNB and the SeNB. It is also possible to support press scheduling for the MeNB and the SeNB simultaneously. The press scheduling settings for the MeNB and the SeNB may be the same.

[0628] In the setting of the SPS of the 2nd-eNB in the split bearer, the method disclosed in the above-described embodiment may be applied.

[0629] By doing so, it becomes possible to set press scheduling for the SeNB as well. Therefore, it is possible to shorten the time to start transmitting uplink data for the SeNB as well, so that the reduction in the uplink transmission delay as a bearer can be increased.

[0630] The press scheduling setting in the MeNB and the press scheduling setting in the SeNB may be different. For each eNB of the MeNB and the SeNB, press scheduling may be set separately, that is, independently.

[0631] In DC, since the split configuration can be set for each bearer, the data transmitted for each eNB is different. For example, for bearer #1, a split bearer using the MeNB and SeNB can be set, and for bearer #2, a non-split bearer that is not a split bearer using the MeNB can also be set. Therefore, since the data transmitted for each eNB set in DC is different, the amount of delay required for each eNB set in DC is also different.

[0632] As described above, by enabling independent press scheduling to be set for each eNB, it becomes possible to set press scheduling considering the bearer configuration. As a result, it becomes possible to satisfy the amount of delay required for each eNB for which DC is set.

[0633] It may be possible to independently set the press scheduling for each eNB for each bearer. For example, in the above example, it may be possible to independently set the press scheduling for the MeNB and SeNB of bearer #1 and the press scheduling for the MeNB of bearer #2. In this way, by making it possible to independently set the press scheduling for each eNB for each bearer, it becomes possible to satisfy different required delay amounts depending on the bearer.

[0634] Disclose the entity that sets the press scheduling and the method of notifying the UE of the press scheduling setting.

[0635] The MeNB performs the pre-scheduling configuration. The MeNB performs the pre-scheduling configuration for both the MeNB and the SeNB. The MeNB notifies the SeNB of the pre-scheduling configuration of the SeNB. The configuration may include cancellation. The SeNB may determine the approval (permission / non-permission) for the pre-scheduling configuration notified by the MeNB. When the SeNB approves the pre-scheduling configuration notified by the MeNB, the SeNB may notify the MeNB of the information indicating approval. When the SeNB disapproves the pre-scheduling configuration notified by the MeNB, the SeNB may notify the MeNB of the information indicating disapproval.

[0636] When the MeNB receives a notification of disapproval from the SeNB, the MeNB may change the pre-scheduling configuration and notify the SeNB again. The re-configuration may be repeated until a notification of approval is received from the SeNB.

[0637] For the notification of the pre-scheduling configuration between the MeNB and the SeNB, the X2 interface may be used. It may also be notified included in the message for addition, cancellation or modification of the SeNB. For the notification of the information indicating approval / non-approval between the SeNB and the MeNB, the X2 interface may be used.

[0638] The MeNB notifies the UE of the pre-scheduling configuration for at least one of the MeNB and the SeNB. For the notification of the pre-scheduling configuration, the Uu interface may be used. The pre-scheduling configuration may also be notified included in the message for setting the DC.

[0639] As another method, the SeNB may perform the pre-scheduling configuration of the SeNB. The SeNB notifies the UE of the pre-scheduling configuration.

[0640] Alternatively, the SeNB may notify the MeNB of the pre-scheduling configuration of the SeNB. The pre-scheduling configuration may be notified using the X2 interface. The MeNB that has received the pre-scheduling configuration of the SeNB from the SeNB may notify the UE of the configuration.

[0641] The pre-scheduling configuration highly depends on the bearer configuration. Therefore, it is more preferable that the MeNB that configures DC using the information set for the bearer performs the pre-scheduling configuration.

[0642] By using the method disclosed in this embodiment, pre-scheduling can be performed even when DC is configured for the UE to communicate by connecting to two eNBs.

[0643] Thereby, it is possible to increase the communication capacity and reduce the uplink transmission delay, enabling high-capacity communication in a shorter time.

[0644] In this embodiment, a method for configuring pre-scheduling when DC is configured for the UE is disclosed. When DC is not configured for the UE but is to be configured for the UE, the pre-scheduling may be configured for the SeNB. The eNB may configure the pre-scheduling for the SeNB when adding the SeNB. The method disclosed in this embodiment may be appropriately applied to this pre-scheduling configuration.

[0645] By doing so, in the process of adding the SeNB, it is possible to omit the scheduling request process that the UE has conventionally performed for the SeNB. Thereby, it is possible to reduce the time required for the scheduling request, so that the time for configuring DC can be shortened. Also, the delay in communication can be reduced, enabling high-capacity communication in a shorter time.

[0646] The method disclosed in this embodiment can be applied not only when adding a SeNB but also when modifying a SeNB. For the modified SeNB, the pre-scheduling method disclosed in this embodiment may be appropriately applied. Thereby, the same effects as in this embodiment can be obtained.

[0647] In the above embodiments and their modifications, the case where split bearers are supported in dual connectivity (DC) has been disclosed. The present disclosure is applicable not only to DC but also to multi-connectivity in which communication is performed using a plurality of eNBs. When split bearers are performed in multi-connectivity, it may be applied when uplink data is not transmitted to one or more of the eNBs constituting the multi-connectivity according to a predetermined rule. Thereby, the same effects as in the above embodiments and their modifications can be obtained.

[0648] In the above embodiments and their modifications, the case where SPS is set when a UL split bearer is set and DRAT is used has been disclosed, but it may also be applied when dynamic scheduling is performed instead of when SPS is set. The method for setting the DRAT threshold and the method related to padding transmission in the case where SPS is set when DRAT is used may also be applied when dynamic scheduling is performed when DRAT is used.

[0649] For example, when the DRAT threshold is set, when the 2nd-eNB notifies the UE of an uplink grant by dynamic scheduling and no uplink transmission data is generated at the UE on the resource of the uplink grant, the same problem as in the case where SPS is set occurs. Also, when the DRAT threshold is set, the same problem occurs when no uplink transmission data is generated at the UE on the pre-scheduled resource when dynamic scheduling by pre-scheduling is performed at the 2nd-eNB.

[0650] To solve such problems, the methods disclosed in Embodiment 1, Embodiment 2, Modification 1 of Embodiment 2, Embodiment 5, Embodiment 7, Embodiment 8, Modification 1 of Embodiment 8, and Modification 2 of Embodiment 8 may be appropriately applied. Even when dynamic scheduling is performed when DRAT is used, the same effects can be obtained.

[0651] Embodiment 12. When the eNB and the UE communicate, there is a technique in which the eNB uses a plurality of antennas and transmits a signal using beamforming that forms a beam only in the direction of the UE, which is the communication target terminal. As a method of covering the service area of the eNB using beamforming, there is a method of arranging a plurality of beams with fixed directions. In this case, the eNB switches the fixed beam according to the movement of the UE and uses an appropriate beam.

[0652] FIG. 26 is a diagram for explaining beamforming using a multi-element antenna. The eNB configures the antenna 408 shown in FIG. 4 with a multi-element antenna 2401.

[0653] The eNB forms a beam only in a predetermined direction using some or all of the plurality of antennas of the multi-element antenna 2401 and communicates with the UE 2402 that is the communication target. As shown in FIG. 26, the coverages 2403, 2404, 2405 of the respective beams formed using beamforming are narrow coverages. The eNB covers the service area by forming a plurality of beams having narrow coverages fixed in different directions.

[0654] When the UE 2402 is present in the coverage 2403 of the first beam, the eNB communicates with the UE 2402 using the first beam. When the UE 2402 moves to the coverage 2404 of the second beam, the eNB switches from the first beam to the second beam and communicates with the UE 2402. Hereinafter, the beam before switching may be referred to as the "source beam", and the beam after switching may be referred to as the "target beam".

[0655] When beamforming is used, the service area configured by the eNB is divided into narrow coverages configured by a plurality of beams. Therefore, fast beam switching processing is required for the movement between the beams of the UE.

[0656] The eNB may form a plurality of beams using beamforming for each cell. In such a case, beam switching processing occurs during the movement between the beams of the UE within one cell.

[0657] In the beam switching process, the UE synchronizes with the target beam, and the eNB must schedule the radio resources of the target beam for the UE. Therefore, it is required to enable the acceleration of the beam switching process during the movement between the beams of the UE and provide a high-speed and stable communication system.

[0658] In order to accelerate the beam switching process, it is effective to shorten the time required for such synchronization processing and radio resource scheduling processing.

[0659] In the present embodiment, a method for shortening the time of synchronization processing with the target beam and radio resource scheduling processing in the target beam is disclosed.

[0660] For the synchronization process with the target cell, the conventional synchronization method with the cell may be applied. The UE receives at least one of the synchronization signal, reference signal, and discovery signal transmitted in the target beam to synchronize with the target beam. For example, when synchronization signals such as P-SS and S-SS used in the conventional cell are used as the synchronization signal, synchronization may be performed using the synchronization signal. In this case, at least a period of 6 subframes is required for synchronization.

[0661] The synchronization signals used in conventional cells are assigned synchronization codes that correspond one-to-one to the PCI for each cell. However, with the PCI for each cell, the UE cannot recognize with which beam it has synchronized. To solve such a problem, an identifier for each beam may be provided, and a code corresponding one-to-one to the identifier for each beam may be assigned to the synchronization signal of each beam.

[0662] By doing so, the UE can recognize with which beam it has synchronized. The identifier for each beam may be assigned by being superimposed on the identifier for each cell. The UE can recognize which cell it is, and furthermore, can recognize which beam it is.

[0663] Similarly, a code corresponding one-to-one to the identifier for each beam may be assigned to the reference signal and the discovery signal. The UE can recognize which beam the received beam is by receiving the reference signal or the discovery signal and obtaining the identifier for each beam.

[0664] However, when applying the synchronization process with a conventional cell, as described above, for example, when using a synchronization signal, at least a period of 6 subframes is required until the UE receives the synchronization signal. Considering the time required for the synchronization process in the UE, the time required for the synchronization process with a conventional cell further increases. A method for shortening the time required for these synchronization processes is disclosed.

[0665] The eNB synchronizes between the beams within the same cell. It may be assumed that the beams within the eNB are synchronized. More specifically, subframe timing synchronization and slot timing synchronization are performed between the beams. Also, the SFN (System Frame Number), radio frame number, and slot number may be synchronized.

[0666] By doing so, even if beam switching processing is performed on the UE, there is no need to synchronize with the target beam. Therefore, it becomes possible to reduce the time required for synchronization processing.

[0667] Disclosed is a method for shortening the processing time of scheduling of radio resources in a target beam. The scheduling information of downlink radio resources is included in downlink control information (DCI). The downlink control information is notified to the UE by an L1 / L2 control signal. In LTE, it is mapped to PDCCH or EPDCCH. An identifier (C-RNTI) individually assigned to the UE for each cell is masked on the CRC of the L1 / L2 control signal. By detecting its own C-RNTI, the UE can receive the L1 / L2 control signal addressed to itself and obtain the downlink control information, and can obtain the scheduling information of the downlink radio resources.

[0668] In the beam within the cell, the same identifier may be used for the UE-specific identifier masked on the CRC of the L1 / L2 control signal. The identifier individually assigned to the UE for each cell may be used. By doing so, even if beam switching processing is performed within the cell, the UE can use the C-RNTI used in the source beam also in the target beam.

[0669] Therefore, after synchronizing with the target beam, it becomes possible to receive the scheduling information by immediately receiving the L1 / L2 control signal.

[0670] In the beam switching process across cells, the eNB may notify the UE of the C-RNTI in advance. The eNB may notify the UE of the C-RNTI using the source beam. By doing so, also in the beam switching process between cells, after synchronizing with the target cell, it becomes possible to immediately receive the L1 / L2 control signal and receive the scheduling information.

[0671] As another method, an identifier (referred to as B-RNTI) may be provided to be individually assigned to each UE for each beam. The identifier individually assigned to each UE for each beam may be masked in the CRC of the L1 / L2 control signal. In the beam switching process, the eNB may notify the UE of the B-RNTI in advance. The eNB may notify the UE of the B-RNTI using the source beam. By doing so, in the beam switching process, after synchronization with the target cell, it becomes possible to immediately receive the L1 / L2 control signal and receive the scheduling information.

[0672] By individually assigning B-RNTI to each UE for each beam, it is no longer necessary to make the control different between the switching of beams within a cell and the switching of beams between cells. Therefore, it becomes possible to facilitate the control in the eNB and the UE. Also, since it is no longer necessary to determine which control to perform, it becomes possible to reduce the time required for the determination.

[0673] The scheduling information of the uplink radio resources is also similarly included in the downlink control information (DCI). Therefore, the method disclosed above can be applied.

[0674] In the uplink, the UE needs to request radio resources from the eNB. In a conventional cell, the request for radio resources is made by a scheduling request (SR) or a PRACH. In the beam switching process, the UE makes a request for radio resources for the target beam.

[0675] However, SR and PRACH cannot be performed at arbitrary timings and must be performed at predetermined timings set by the eNB. Therefore, the UE has to wait until the predetermined timings set by the eNB, resulting in a delay. In the case of beam switching processing with narrow coverage, this delay is likely to lead to communication failure.

[0676] Disclose a method for solving such problems. In advance, the eNB schedules the uplink radio resources in the target beam for the UE. In advance, the eNB may schedule the uplink radio resources in the target beam for the UE using the source beam.

[0677] For example, as a method for scheduling the uplink radio resources of the target beam, it is advisable to use SPS. The eNB may notify the UE of the setting of the uplink SPS in the target beam using the source beam. The notification of the setting of the uplink SPS may be performed before the UE synchronizes with the target beam. The UE that has received the setting of the uplink SPS in the target beam performs uplink transmission using the notified setting of the uplink SPS in the target beam after synchronizing with the target beam.

[0678] As the setting of the SPS, not only the time interval of the SPS resource but also the offset and scheduling information may be included. As the offset, the radio frame number and the subframe number may be specified.

[0679] Disclose the method for setting and activating the SPS in the target beam. The setting of the time interval of the SPS resource may be performed in the source beam. By setting the time interval of the SPS resource in the source beam, it is possible to eliminate the need for the setting from the target beam during beam switching and shorten the time required for the switching process.

[0680] The setting of the scheduling information of the SPS resource may be performed in the source beam. By setting the scheduling information of the SPS resource in the source beam, it is possible to eliminate the need for the setting from the target beam during beam switching and shorten the time required for the switching process.

[0681] Alternatively, the scheduling information of the SPS resource may be set for the target beam. This enables setting of scheduling information such as resource allocation according to the load status of the target beam.

[0682] Activation and deactivation of SPS may be performed for the source beam. By performing activation and deactivation of SPS for the source beam, it becomes unnecessary to set from the target beam at the time of beam switching, and it is possible to shorten the time required for the switching process.

[0683] Alternatively, activation and deactivation of the SPS resource may be performed for the target beam. This enables activation and deactivation according to the load status of the target beam. Also, it is possible to improve the resource utilization efficiency more than when performing in advance for the source beam. This is because when performing in advance for the source beam, during the period from activating and deactivating in advance for the source beam for the target UE until switching to the target beam and actually performing SPS, the SPS resource must be continuously allocated to the UE, resulting in waste of radio resources.

[0684] The above-described methods of setting SPS, as well as activating and deactivating SPS, for the source beam or the target beam may be used in appropriate combinations. This enables setting according to the load status and delay tolerance of the target beam.

[0685] By doing so, the UE no longer needs to request uplink radio resources for the target beam after beam switching from the eNB, so it is possible to reduce the delay. Therefore, it is possible to shorten the time required for the beam switching process.

[0686] Here, as a method for scheduling the uplink radio resources of the target beam, using uplink SPS has been disclosed. However, as a method for scheduling the downlink radio resources of the target beam, downlink SPS may also be used. The eNB may notify the UE of the setting of downlink SPS at the target beam using the source beam. By doing so, after the UE switches to the target beam, it becomes possible to receive the set SPS resources according to the setting of the downlink SPS.

[0687] As another method for the scheduling method of the uplink radio resources of the target beam, dynamic scheduling may be used. Even if the eNB does not receive a scheduling request from the UE, the eNB transmits radio resource scheduling information to the UE at an arbitrary subframe using the target beam. After the UE synchronizes with the target beam, by receiving the L1 / L2 control signal in each subframe, the UE can receive the radio resource scheduling information transmitted by the eNB at an arbitrary subframe. Thereby, the UE can perform uplink transmission using the received uplink radio resource scheduling information.

[0688] By doing so, the UE no longer needs to make an uplink radio resource request to the eNB, so it becomes possible to reduce the delay. Therefore, it becomes possible to shorten the time for beam switching processing.

[0689] FIG. 27 is a diagram showing an example of a sequence related to a method for shortening the time of beam switching processing in Embodiment 12. FIG. 27 shows the case of switching from the source beam (S-Bm) to the target beam (T-Bm).

[0690] In step ST2501, the eNB communicates with the UE using the source beam. The eNB synchronizes in advance between the source beam and the target beam. Synchronization of subframe timing and slot timing is performed between the source beam and the target beam. Also, synchronization is taken for the SFN (System Frame Number), radio frame number, and slot number. By doing so, in step ST2502, when the UE is synchronized with the source beam, it will also be synchronized with the target beam. In step ST2502, the UE indicates that it is synchronized with the target beam.

[0691] In step ST2503, the eNB notifies the UE of the uplink scheduling information in the target beam using the source beam. Here, the uplink scheduling information in the target beam is the configuration information of the uplink SPS in the target beam. As the SPS configuration information, not only the time interval of the SPS resource but also the offset and scheduling information are included.

[0692] Information regarding the target beam may be notified together with the uplink scheduling information in the target beam. Examples of the information regarding the target beam include the identifier of the target beam. Also, when using an identifier assigned individually to each UE for each beam, the identifier may be notified. Notification of the uplink scheduling information in the target beam and the information regarding the target beam may use RRC signaling.

[0693] In step ST2504, the eNB notifies the UE of a beam switching instruction using the source beam. Beam switching instruction information may be provided and notified. The beam switching instruction information is information that triggers the switching of the beam. In other words, it is information that triggers the UE to receive the L1 / L2 control signal of the target beam. RRC signaling may be used for notification of the beam switching instruction information.

[0694] Since the UE that has received the beam switching instruction information has already been synchronized with the target beam in step ST2502, in step ST2505, the UE receives the downlink control information of the target beam. The UE receives the per-subframe PDCCH or EPDCCH. By receiving the downlink control information of the target beam, the UE can obtain the downlink scheduling information, and according to the scheduling information, it becomes possible to receive the downlink data.

[0695] When there is uplink transmission data, in step ST2506, the UE transmits the uplink data to the eNB using the SPS resource set for the target beam.

[0696] By doing so, in step ST2507, communication becomes possible between the UE and the eNB using the target beam.

[0697] By using the method disclosed in this embodiment, when the UE moves between the beams with narrow coverage due to beamforming and switches the beam, it is possible to reduce the deterioration of communication quality and the interruption of communication caused by the time-consuming synchronization process and radio resource scheduling process.

[0698] When the positions of the antennas composed of a plurality of antenna elements forming the beam are the same for each beam, the distances of the paths from the antennas to the UE are almost the same. Therefore, there is no need to change the uplink transmission timing between the source beam and the target beam. However, when the positions of the antennas are different for each beam, in the target beam, the UE may need to perform uplink synchronization.

[0699] Disclosed is a method for performing uplink synchronization. The eNB gives an instruction to the UE to execute random access (RA) processing in the target beam. The instruction to execute RA processing in the target beam may be given using the L1 / L2 control signal in the target beam. Alternatively, it may be given using PDCCH or EPDCCH in the target beam.

[0700] When the UE receives an instruction to execute RA processing in the target beam, it may perform RA processing in the target beam. By performing RA processing in the target beam, the eNB can adjust the uplink transmission timing of the UE. Specifically, in the RA processing, the uplink transmission timing is notified to the UE. This is also referred to as Timing Advanced.

[0701] In this way, in the target beam, the UE can perform uplink synchronization.

[0702] Disclosed is a method for the eNB to determine whether to perform uplink synchronization. The eNB acquires information regarding the positions of the antennas. For example, each antenna acquires information regarding its own antenna position using a global positioning system (GPS) or the like, and notifies the eNB of the information regarding its own antenna position. Alternatively, the operator sets the information regarding the antenna position in the eNB. Alternatively, the operator may set the information regarding the antenna position in the OAM, and the OAM may notify the eNB.

[0703] The eNB determines whether uplink synchronization is necessary for the UE that is the target of communication using the target beam, using the acquired information regarding the positions of the antennas.

[0704] When the eNB determines that uplink synchronization is necessary, it may give an instruction to the UE to execute RA processing in the target beam.

[0705] By doing so, the eNB can determine whether to perform uplink synchronization as needed. If uplink synchronization is not required, the RA process can be skipped. Also, even if uplink synchronization is required, since the RA process is performed upon instruction from the eNB, the RA process will be collision-free and the control can be simplified.

[0706] In the example shown in FIG. 27, the uplink scheduling information in the target beam and the switching instruction to the target beam were notified by separate signaling. As another example, the uplink scheduling information in the target beam and the switching instruction to the target beam may be notified by the same signaling. By doing so, a similar effect can be obtained.

[0707] Embodiment 13. In Embodiment 12, it was disclosed that the eNB notifies the UE of a beam switching instruction for causing the UE to perform beam switching. For example, the process of step ST2504 in FIG. 27 was shown.

[0708] In Embodiment 12, it was disclosed that RRC signaling is used for notifying beam switching instruction information. However, when RRC signaling is used, since it is divided into a plurality of transport blocks, it will be transmitted in a plurality of transmission time intervals (TTIs). Also, retransmission is applied for each transport block. Therefore, the time required for the transmission and reception of RRC signaling will increase. In this embodiment, a method for shortening the time required for notifying a beam switching instruction in the beam switching process is disclosed.

[0709] The beam switching instruction is performed by MAC signaling or L1 / L2 signaling. As the L1 / L2 signaling, an individual control channel is used. For example, it is PDCCH or EPDCCH, etc. Since both the MAC signaling and the L1 / L2 signaling are performed in 1 TTI, it is possible to shorten the time taken for the beam switching instruction compared to the RRC signaling.

[0710] In the case of MAC signaling, HARQ is applied. Therefore, an effect that the reception error rate becomes lower can be obtained compared to the case of using the L1 / L2 signaling.

[0711] In the case of L1 / L2 signaling, HARQ is not applied. Therefore, it is possible to notify the beam switching instruction with low latency compared to the case of using the MAC signaling.

[0712] Whether to use the MAC signaling or the L1 / L2 signaling may be statically determined by a standard or the like. Alternatively, both methods may be supported and used selectively in a semi-static or dynamic manner. For example, depending on the radio wave propagation environment, the MAC signaling or the L1 / L2 signaling method may be selectively used. When the radio wave propagation environment is good, the L1 / L2 signaling may be used, and when the radio wave propagation environment is not good, the MAC signaling may be used.

[0713] The entity that determines the beam switching is disclosed. The MAC protocol in the eNB may determine the beam switching. By having the MAC, instead of the RRC, make the determination, it becomes possible to include the determination of which beam to use together with the scheduling or in the scheduling. Each beam may be treated as a radio resource configured on the same time-frequency axis. A plurality of beams may be treated as a plurality of radio resources, and scheduling using the plurality of radio resources may be performed.

[0714] In addition, making the MAC the entity that determines beam switching is suitable for notifying beam switching instructions using signaling below the MAC layer. By making the MAC the entity that determines beam switching, it becomes possible to shorten the processing time from beam switching determination to transmission of beam switching instructions.

[0715] In addition to beam switching instructions, three specific examples of information used when causing the UE to perform beam switching are disclosed below. Hereinafter, the information used when causing the UE to perform beam switching may be referred to as "beam switching related information".

[0716] (1) Information on which beam to switch to. For example, the identifier of the target beam.

[0717] (2) Information on resetting each protocol of the source beam and setting each protocol of the target beam.

[0718] (3) Information for enabling communication on the target beam.

[0719] Regarding the above specific example (1), a more specific explanation will be given. It may be allocated for each predetermined range of the network. For example, it may be allocated for each MME. Alternatively, it may be allocated for each eNB. Alternatively, the beam identifier may be allocated for each cell. Alternatively, a predetermined number of beam identifiers may be prepared in advance and allocated from among them.

[0720] By allocating in a narrow range of the network, it becomes possible to reduce the amount of information required for the beam identifier, for example, the number of bits. For example, by allocating the beam identifier for each cell, it becomes possible to reduce the amount of information, for example, the number of bits, of the beam switching related information.

[0721] Regarding the above specific example (2), it will be further specifically described. Between the beams within the same cell, the same PDCP is used. Therefore, information on whether to perform at least one of resetting and reconfiguring PDCP upon beam switching is unnecessary. It may be determined in advance in a standard or the like that neither resetting nor reconfiguring is to be performed. The UE may hold the PDCP configuration of the source beam in the beam switching process within the same cell.

[0722] Between the beams within the same cell, the same RLC is used. Therefore, information on whether to perform at least one of resetting and reconfiguring RLC upon beam switching is unnecessary. It may be determined in advance in a standard or the like that neither resetting nor reconfiguring is to be performed. The UE may hold the RLC configuration of the source beam in the beam switching process within the same cell.

[0723] The beams within the same cell differ only in some of the MAC configurations. Therefore, information on whether to perform at least one of resetting and reconfiguring MAC upon beam switching is unnecessary. That is, resetting is unnecessary, and only the different configurations may be reconfigured. It may be determined in advance in a standard or the like that only the different configurations are to be reconfigured. The UE may hold only the MAC configuration identical to that of the source beam in the beam switching process within the same cell.

[0724] The beams within the same cell have some or all of the PHY configurations different. Information on whether to perform at least one of resetting and reconfiguring PHY is required.

[0725] As specific examples of the information for enabling communication with the target beam in the above specific example (3), three examples of (3-1) to (3-3) below are disclosed.

[0726] (3-1) UE identifier for the target beam. For example, C-RNTI, or B-RNTI.

[0727] (3-2) Information regarding the MAC and PHY of the target beam. For example, there are common radio resource settings, main MAC settings, individual PHY settings, etc. As parameters for the common radio resource settings, "radioResourceConfigCommon" is used. As parameters for the main MAC settings, "mac-MainConfig" is used. As parameters for the individual PHY settings, "physicalConfigDedicated" is used.

[0728] (3-3) Information regarding the SCell in the target beam.

[0729] For the information in the above (3-1) to (3-3), those that do not change from the source beam settings may be omitted. It may also be sufficient to notify only those that have changed from the source beam settings. This can reduce the amount of information.

[0730] In addition to the beam switching instruction, by notifying the UE of the information used when causing the UE to perform beam switching from the eNB, the UE that has received the beam switching instruction information can communicate using the target beam.

[0731] The eNB notifies the UE of beam switching related information in order to cause the UE to perform beam switching. A method for notifying the beam switching related information is disclosed.

[0732] The eNB uses the source beam to notify the UE of the beam switching related information. The beam switching related information is notified before notifying the beam switching instruction. The beam switching related information may be notified by RRC signaling. A new message may be newly established for notifying the beam switching related information.

[0733] A message for notifying beam measurement configuration information (hereinafter sometimes referred to as "beam measurement configuration information") may be provided. The beam measurement configuration information may also be CSI measurement configuration information.

[0734] The UE measures beams using the beam measurement configuration information notified by the eNB. The UE measures the beams included in the beam measurement configuration information. The UE reports the beam measurement results to the eNB. The settings for reporting may also be notified by the eNB to the UE. It may be notified together with the beam measurement configuration information or included in the beam measurement configuration information. The eNB receives the report of the beam measurement results from the UE and determines the beam to be used for the UE.

[0735] Disclose the method for the UE to report the beam measurement results to the eNB. As the beam measurement, measure the received power of the reference signal or the discovery signal transmitted for each beam. Or it may be the received quality. Or, measure the quantity including the interference power and the noise power. For example, the signal to noise ratio (SNR), the signal to interference plus noise power ratio (SINR), etc.

[0736] The reporting of the measurement results of the conventional cell is performed by RRC signaling. It may be performed by RRC signaling, but in the case of RRC signaling, as described above, the time required for the transmission and reception of RRC signaling becomes large.

[0737] As another method, it may be notified by MAC or L1 / L2 signaling. It may be notified using MAC CE. Or it may be notified by mapping to PUCCH. Or it may be notified by mapping to PUSCH. Or CQI reporting or CSI reporting may be used.

[0738] By doing so, it becomes possible for the UE to report the beam measurement results to the eNB earlier. As a result, it becomes possible to shorten the period from the beam measurement to the beam switching process, so that the eNB can select a more appropriate target beam.

[0739] FIG. 28 is a diagram showing an example of a sequence related to a method for shortening the time of beam switching processing in Embodiment 13. FIG. 28 shows a case of switching from a source beam (S-Bm) to a target beam (T-Bm). A case of synchronization between the source beam and the target beam is shown. A case of notifying in advance the scheduling information of radio resources in the target beam using the source beam is shown. Since the sequence shown in FIG. 28 is similar to the sequence shown in FIG. 27, the same step numbers are assigned to the same steps, and common explanations are omitted. Here, mainly different parts will be described.

[0740] In step STST2601, the eNB notifies the UE of beam measurement configuration information using the source beam. RRC signaling is used for the notification of the beam measurement configuration information.

[0741] The UE that has acquired the beam measurement configuration information from the eNB measures, in step ST2602, the reference signal transmitted for each beam for the measurement beams included in the beam measurement configuration information.

[0742] In step ST2603, the UE notifies the eNB of the measurement result obtained in step ST2602 using the source beam. L1 / L2 signaling may be used for the notification of the measurement result. For example, it is reported using PUCCH which is an uplink control channel. Thereby, the speed of signaling can be increased.

[0743] In step ST2603, the UE does not necessarily report all the measurement results obtained in step ST2602. Only the measurement results of the beams for which the reporting has been triggered may be reported according to predetermined criteria. The eNB notifies these settings to the UE together with the beam measurement configuration information in step ST2601.

[0744] The eNB that received the report of the beam measurement result in step ST2603 determines in step ST2604 whether to perform beam switching for the UE. For example, if the reception quality of the source beam deteriorates below a predetermined threshold and there is a beam with better reception quality than the source beam, the eNB determines to switch to the beam with good reception quality.

[0745] The eNB that determined to perform beam switching for the UE in step ST2604 notifies the UE of the beam switching related information for the target beam using the source beam in step ST2605. RRC signaling may be used for the notification of the beam switching related information.

[0746] In step ST2503, if the eNB notifies the UE of the scheduling information of the uplink radio resources in the target beam using the source beam, the notification may be made with the same signaling.

[0747] In step ST2606, the eNB notifies the UE of the beam switching instruction information to the target beam using the source beam. MAC signaling is used for the notification of the beam switching instruction information. Thereby, the signaling speed can be increased.

[0748] The UE that received the beam switching related information of the target beam in step ST2605 and received the beam switching instruction information in step ST2606 receives the L1 / L2 control signal of the target beam.

[0749] The eNB that transmitted the beam switching instruction information to the target beam to the UE in step ST2606 performs scheduling for the UE using the target beam.

[0750] In the sequence shown in FIG. 28, the beam switching related information and the message for notifying the beam measurement configuration information were notified separately. As another method, the beam switching related information may be included in the message for notifying the beam measurement configuration information and notified. It is preferable to include the beam switching related information of the beam included in the beam measurement configuration information. In this case, it will be notified to the UE before the eNB determines the target beam. Therefore, the target beam included in the beam switching related information has not yet been determined. Therefore, it is preferable to include information about the beam for beam measurement instead of the target beam. The beam for beam measurement may be one or plural. The source beam may be included.

[0751] Also, for example, when the target beam is not determined by the first beam measurement configuration information, the eNB may notify the UE of other beam measurement configuration information again. It is preferable to include the beam switching related information in the message for notifying the beam measurement configuration information and notify it.

[0752] Although it has been disclosed to use RRC signaling for notifying the beam switching related information from the eNB to the UE, as another method, MAC signaling may be used. It may be notified by MAC CE. A new MAC CE may be provided to include the information necessary for executing the beam switching. It may be notified together with the beam switching instruction information.

[0753] The information notified by RRC signaling and the information notified by MAC signaling may be separated. For example, information with a large amount of information is notified by RRC signaling, and information with a small amount of information is notified by MAC signaling. The setting information for enabling communication with the target beam in the above-mentioned specific example (3) may be notified by RRC signaling, and the identifier of the target beam in the above-mentioned specific example (1) may be notified by MAC signaling. By notifying the information with a small amount of information by MAC signaling, the beam switching instruction information can also be transmitted in one transport block.

[0754] When the beam switching instruction information is notified by MAC signaling, the MAC signaling will be performed in 1 TTI. As described above, since the RRC signaling is transmitted after being divided into a plurality of transport blocks, it will be performed over a plurality of TTIs. Further, even considering retransmission, by using the MAC signaling, it is possible to shorten the time required for notifying the beam switching instruction information as compared with the case of using the RRC signaling.

[0755] Therefore, by using the method disclosed in the present embodiment, when the UE moves between the beams with narrow coverage due to beamforming and switches the beam, it is possible to reduce the deterioration of the communication quality and the disconnection of the communication due to the time taken for signaling.

[0756] Also, by using the L1 / L2 signaling for reporting the measurement results of the beam, it is possible to shorten the time from the measurement of the beam to the switching of the beam. As a result, it becomes possible to switch the beam to a more optimal beam, and it is possible to reduce the deterioration of the communication quality and the delay and disconnection of the communication due to the failure of the switching.

[0757] Embodiment 13 Modification 1. In Embodiment 13, a method for shortening the time required for notifying the beam switching instruction information was disclosed. In this modification, another method is disclosed.

[0758] The eNB determines one or more beams that are candidates for the target beam for the UE to be communicated with. The source beam may be included in the candidates for the target beam. Hereinafter, the beam that is a candidate for the target beam may be referred to as a "target candidate beam".

[0759] The eNB determines the activation and deactivation of some or all of the target candidate beams.

[0760] The eNB notifies the UE of the activation or deactivation instructions for some or all of the target candidate beams. This notification is performed using the source beam. MAC signaling or L1 / L2 signaling may be used for this notification.

[0761] The UE synchronizes to the beam that has received the activation instruction and receives downlink control information (DCI). It may also be assumed that the UE receives L1 / L2 control signals. For example, the UE receives PDCCH or EPDCCH. The UE receives PDCCH or EPDCCH and detects DCI addressed to the UE using C-RNTI or B-RNTI.

[0762] If there are multiple beams that have received the activation instruction, the UE will receive the downlink control information of the multiple beams.

[0763] The eNB determines from among the beams for which the UE uses the activated beam and switches from the source beam to the determined beam. The eNB communicates with the UE using the switched beam. At this time, the eNB does not need to notify the UE of the beam switching instruction information. This is because the UE is receiving the downlink control information of the beam that has received the activation instruction, and no matter which beam the communication starts with, it is possible to obtain the scheduling information for this communication.

[0764] By doing so, it is possible to eliminate the need to notify the beam switching instruction information. After the eNB determines the beam switching for the UE, it can immediately communicate with the UE using the switched beam. Therefore, it is possible to shorten the time required for the beam switching process.

[0765] After the eNB determines the target candidate beam, it is advisable to notify the UE of the related information for beam switching of the target candidate beam. The method disclosed in Embodiment 12 can be applied to the notification of the related information for beam switching.

[0766] The determination of the target candidate beam is performed as appropriate. The determination of the target candidate beam may be performed periodically or may be performed according to the report of the measurement result of the UE's beam. When the target candidate beam is changed, it is advisable to notify the UE of the beam switching related information of the target candidate beam again. Only the beam switching related information of the beam to be changed, deleted or added may be notified. Regarding the beam to be deleted, only the beam identifier may be notified.

[0767] The determination of the activation or the beam to be activated is performed as appropriate. The determination of the activation or the beam to be activated may be performed periodically or may be performed according to the report of the measurement result of the UE's beam. When the beam to be activated or deactivated is changed, it is advisable to notify the UE of the instruction of beam activation or deactivation again. Only the beam to be changed may be notified.

[0768] The determination of the beam to be used for the UE is performed as appropriate. The determination of the beam to be used for the UE may be performed periodically or may be performed according to the report of the measurement result of the UE's beam. Thus, even if the beam to be used for the UE is changed, it is not necessary to notify the beam switching instruction information.

[0769] FIG. 29 and FIG. 30 are diagrams showing an example of a sequence related to a method for shortening the time of beam switching processing in Modification 1 of Embodiment 13. FIG. 29 and FIG. 30 are connected at the position of the boundary line BL1. FIGS. 29 and 30 show the case of switching from the source beam (S-Bm) to the first target beam (T-Bm1). Further, the case of switching from the first target beam (T-Bm1) to the second target beam (T-Bm2) is also shown. Further, the case where synchronization is not taken between the source beam and the target beam is shown. Further, the case where the scheduling information of the radio resources in the target beam is not performed in advance using the source beam is shown. The sequences in FIGS. 29 and 30 are similar to the sequence shown in FIG. 28, so the same step numbers are assigned to the same steps, and the common explanations are omitted. Here, mainly the different parts will be described.

[0770] The eNB that has received the report of the beam measurement result in step ST2603 determines, using the report of the beam measurement result from the UE, a beam that is a candidate for the target beam for the UE in step ST2801. For example, two beams with the measurement result of the reception quality of the UE beam being equal to or higher than a predetermined threshold are selected, and three beams including the source beam are determined as target candidate beams. The eNB may consider not only the report of the beam measurement result but also other information in determining the target candidate beam.

[0771] The eNB that has determined the target candidate beam for the UE in step ST2801 notifies the UE of the beam switching related information of the target candidate beam using the source beam in step ST2802. The beam switching related information of the target candidate beam is notified, for example, using RRC signaling.

[0772] In step ST2820, the eNB determines a beam from among the target candidate beams that performs at least one of activation and deactivation for the UE. This determination may use the report of the beam measurement results from the UE received most recently.

[0773] In step ST2803, the eNB notifies the UE of a beam that performs at least one of activation and deactivation. The beam that performs at least one of activation and deactivation is notified, for example, using MAC signaling. Here, the beams to be activated are defined as the source beam (S-Bm), the first target beam (T-Bm1), and the second target beam (T-Bm2).

[0774] The UE that has received a beam that performs at least one of activation and deactivation in step ST2803 synchronizes with the beam to be activated in steps ST2804, ST2805, and ST2806.

[0775] Furthermore, the UE receives downlink control information in the beam to be activated in steps ST2807, ST2808, and ST2809. For example, the UE receives the EPDCCH of the source beam, the first target beam, and the second target beam. It is advisable to use the beam switching related information of the target candidate beam obtained in step ST2802 for these receptions.

[0776] In step ST2810, the eNB determines the beam switching. Specifically, the eNB determines the switching from the source beam to the first target beam. This determination may use the report of the beam measurement results from the UE received most recently.

[0777] In ST2810, the eNB that has determined the beam switching to the first target beam transmits, in step ST2811, scheduling information for the UE to the UE using the first target beam. Examples of the scheduling information include DCI. The DCI includes at least one of downlink scheduling information and uplink scheduling information. Also, downlink data may be transmitted in the same subframe as the downlink scheduling information.

[0778] The UE that has received the downlink control information of the first target beam in step ST2808 acquires, in step ST2811, the scheduling information transmitted using the first target beam.

[0779] The UE that has acquired the scheduling information of the first target beam in step ST2811 receives downlink data according to the downlink scheduling information if the downlink scheduling information is included in the scheduling information.

[0780] The UE that has acquired the scheduling information of the first target beam in step ST2811 transmits uplink data to the eNB according to the uplink scheduling information in step ST2812 if the uplink scheduling information is included in the scheduling information. Alternatively, a scheduling request may be transmitted. Alternatively, a buffer status report (BSR) may be transmitted.

[0781] In this way, the UE and the eNB can communicate using the first target beam in step ST2813.

[0782] In FIGS. 29 and 30, a method for further switching the target beam is disclosed. Communication with the UE in step ST2813 is performed using the first target beam. Therefore, the first target beam becomes the source beam for the UE, but here it will continue to be referred to as the first target beam.

[0783] In step ST2814, the UE performs beam measurement. For this beam measurement, the beam measurement settings included in the beam measurement configuration information notified in step ST2601 are used. Although not shown in the figure, when new beam measurement settings are notified using the first target beam, the measurement may be performed using the beam measurement settings of the beam.

[0784] In step ST2814, the UE that has performed beam measurement reports the beam measurement result to the eNB in step ST2815. This report is performed using the first target beam. L1 / L2 signaling may be used for this report. This can speed up the signaling.

[0785] The eNB that has received the report of the beam measurement result in ST2815 determines the beam switch in step ST2816. The beam switch is performed from the beams to be activated notified to the UE in step ST2803.

[0786] The eNB that has determined to switch the beam to the second target beam in step ST2816 transmits scheduling information for the UE to the UE using the second target beam in step ST2817. Examples of the scheduling information include DCI. The DCI includes at least one of downlink scheduling information and uplink scheduling information. Also, downlink data may be transmitted in the same subframe as the downlink scheduling information.

[0787] The UE that has received the downlink control information of the second target beam in step ST2809 acquires the scheduling information transmitted using the second target beam in step ST2817.

[0788] The UE that has obtained the scheduling information of the second target beam in ST2817, if the downlink scheduling information is included in the scheduling information, receives downlink data according to the downlink scheduling information.

[0789] The UE that has obtained the scheduling information of the second target beam in step ST2817, if the uplink scheduling information is included in the scheduling information, in step ST2818, transmits uplink data to the eNB according to the uplink scheduling information. Alternatively, a scheduling request may be transmitted. Alternatively, a buffer status report (BSR) may be transmitted.

[0790] In this way, the UE and the eNB can communicate using the second target beam in step ST2819.

[0791] By doing so, it becomes possible to switch the beam without notifying the UE of the beam switching instruction information.

[0792] Therefore, it becomes possible to shorten the time from the beam switching decision in the eNB until the UE can switch to the determined beam and communicate.

[0793] As a result, even in a situation where beam switching occurs frequently, it becomes possible to switch to a more optimal beam in a short time, and it becomes possible to reduce the deterioration of communication quality and the delay and interruption of communication due to switching failure.

[0794] Also, by notifying the UE of the beams that are candidates for the target beam, the UE can limit the number of beams for synchronizing and receiving control information. Therefore, the method disclosed above can reduce the processing load of the UE, and it becomes possible to achieve low power consumption, small size and light weight, and low cost.

[0795] In the examples disclosed above, the beams to be activated or deactivated are some or all of the target candidate beams.

[0796] As another method, the beam to be activated may be the same as the target candidate beam. In this case, the determination process of the beam to be activated in the eNB becomes unnecessary.

[0797] Also, in this case, the notification of the related information for switching the target candidate beam may be used as the notification of the activation of the target candidate beam.

[0798] The UE synchronizes with the beam notified by the related information for switching the target candidate beam as the activated beam, and receives the downlink control information.

[0799] For example, the processes of step ST2820 and step ST2803 in FIGS. 29 and 30 are omitted.

[0800] By doing so, it is possible to reduce the amount of signaling from the eNB to the UE. Also, the control in the eNB and the UE can be simplified.

[0801] The UE may set the number of beams that can be received at maximum. The number of beams that can be received at maximum may be determined according to the UE capability. Alternatively, the number of beams that can be received at maximum may be provided as a parameter of the UE capability.

[0802] The UE may notify the eNB in advance of the number of beams that can be received at maximum. The notification of the UE capability may also be used.

[0803] By doing so, the eNB can set the number of target candidate beams or the number of beams to be activated to be equal to or less than the number of beams that the UE can receive at maximum.

[0804] The downlink control information of a certain beam may include the scheduling information of other beams. For example, the downlink control information of the source beam may include the scheduling information of the target beam.

[0805] For example, in FIGS. 29 and 30, the eNB notifies, in step ST2811, the downlink scheduling information or uplink scheduling information of the first target beam using the source beam. The UE receives, in step ST2811, the downlink scheduling information or uplink scheduling information of the first target beam using the source beam. The UE that recognizes that it is the scheduling information of the first target beam receives the radio resources of the first target beam according to the downlink scheduling information in the case of downlink scheduling information. Alternatively, the UE that recognizes that it is the scheduling information of the first target beam transmits using the radio resources of the first target beam according to the uplink scheduling information in the case of uplink scheduling information.

[0806] By doing so, when the UE can use multiple beams, flexible use of multiple beams becomes possible.

[0807] For example, it becomes possible to make the beam for transmitting control information different from the beam for data communication. Operations such as transmitting the control information with one of the multiple beams and performing data communication with the other of the multiple beams are possible. The eNB can use each beam in consideration of the coverage, load, and radio wave propagation status of each beam. For example, the control information may be transmitted with a beam having a wide coverage, and the data communication may be transmitted with a beam having a narrow coverage. By doing so, beam operations suitable for the characteristics of each beam become possible.

[0808] Embodiment 13, Modification 2. When beam switching occurs during the movement between beams of the UE while communication has not yet been successful with the source beam, the problem is how to handle the data for which delivery has not been successful.

[0809] In this modified example, a method for handling data for which delivery has not been successful during beam switching is disclosed. Data for which delivery has not been successful using the source beam is transmitted using the target beam. This may be done for both the uplink and the downlink.

[0810] Disclosed in more detail. Data for which delivery has not been successful using the source beam in PDCP is discarded and transmission is performed again in the target cell. By doing so, it becomes possible to suppress data loss during beam switching.

[0811] When the UE moves between narrow coverage beams formed by beamforming technology, beam switching may occur frequently. In such a case, if the method disclosed above is used, retransmission of PDCP data will be repeated many times. There may also be cases where retransmission of the same PDCP data is repeated many times. Therefore, problems such as delays occurring in data communication and the required QoS not being satisfied will occur. A method for solving such problems is disclosed.

[0812] In beam switching, data being processed in HARQ using the source beam is retransmitted using the target beam. When the UE receives an instruction to move the beam, it retransmits data being processed in HARQ using the source beam using the target beam. When the eNB transmits an instruction to move the beam to the UE, it retransmits data being processed in HARQ using the source beam using the target beam.

[0813] As specific examples of the method of retransmitting data being processed in HARQ using the source beam using the target beam, the following two cases (1) and (2) are disclosed.

[0814] (1) Perform it using the target beam from the first transmission of the data being processed in HARQ.

[0815] (2) HARQ is performed using a source beam and a target beam.

[0816] A specific example of the method of performing from the first transmission of data during HARQ processing in the above specific example (1) using the target beam is disclosed. FIG. 31 is a diagram showing an example of a sequence related to the method of performing from the first transmission of data during HARQ processing in Modification 2 of Embodiment 13 using the target beam. When transmitting uplink data using the target beam, a method performed by the UE from a scheduling request (SR) is shown.

[0817] In step ST2901, the UE is receiving downlink data from the eNB using the source beam.

[0818] In step ST2902, the UE is transmitting uplink data to the eNB using the source beam.

[0819] In step ST2903, the eNB determines a beam switch for the UE.

[0820] In step ST2904, the eNB provides the target beam with the outstanding downlink data information, which is information regarding the downlink data during HARQ processing in the source beam. When the source beam and the target beam are of the same eNB, it is performed within the same eNB. In this case, the information regarding the downlink data during HARQ processing may be applied from the source beam to the target beam.

[0821] The information regarding the downlink data during HARQ processing in the source beam may be information that can identify the data to be transmitted in the target beam.

[0822] In step ST2905, the eNB notifies the UE of beam switch instruction information using the source beam.

[0823] The UE that has received the beam switching instruction information synchronizes with the target beam in step ST2906.

[0824] In step ST2907, the eNB performs downlink scheduling to transmit the downlink data that was in the HARQ process in the source beam from the first transmission using the target beam to the UE. At this time, the eNB may use the information regarding the downlink data in the HARQ process in the source beam received in step ST2904. The notification may use the target beam.

[0825] In step ST2907, the eNB that has notified the UE of the scheduling information in the target beam for the first transmission of data transmits the downlink data in the HARQ process in the source beam to the UE using the target beam according to the scheduling information.

[0826] The UE that has received the downlink scheduling information in step ST2907 receives the downlink data in the HARQ process in the source beam in step ST2908 using the target beam according to the scheduling information.

[0827] By doing so, it becomes possible to communicate the downlink data in the HARQ process in the source beam using the target beam.

[0828] Next, the uplink data is shown. The UE that has received the beam switching instruction information in step ST2905 transmits a scheduling request (SR) to the eNB using the target beam in step ST2909. The SR is transmitted to transmit the uplink data in the HARQ process in the source beam.

[0829] The eNB that has received the SR in ST2909 determines the uplink scheduling and notifies the UE of the uplink scheduling information using the target beam in step ST2910.

[0830] The UE that has received the uplink scheduling information in ST2910 transmits UL data to the eNB in step ST2911 according to the scheduling information. Transmission starts from the first transmission of the uplink data being processed by HARQ in the source beam.

[0831] By doing so, it becomes possible to communicate the data being processed by HARQ in the source beam using the target beam. Therefore, it is not necessary to start from the retransmission of the PDCP data in the target beam. As a result, even when beam switching occurs frequently, it is possible to reduce the occurrence of a state where the retransmission of the PDCP data is repeated many times.

[0832] Another method is disclosed. FIG. 32 is a diagram showing another example of a sequence related to a method of performing transmission from the first transmission of data being processed by HARQ in the target beam in Modification 2 of Embodiment 13. FIG. 32 shows a sequence of a method in which the UE does not require SR transmission when performing uplink data transmission using the target beam. Since the sequence shown in FIG. 32 is similar to the sequence shown in FIG. 31, the same step numbers are assigned to the same steps and the common description is omitted. Here, mainly the different parts will be described. Regarding the downlink data, since it is the same as in FIG. 31, the description is omitted, and the uplink data will be described.

[0833] In step ST2903, the eNB that has determined the beam switch for the UE provides information regarding the uplink data being processed by HARQ in the source beam to the target beam in step ST3001. When the source beam and the target beam are the same eNB, it is performed within the same eNB. In this case, the information regarding the uplink data being processed by HARQ may be applied from the source beam to the target beam.

[0834] The information regarding the uplink data being processed by HARQ in the source beam may be any information that can identify the data to be transmitted in the target beam.

[0835] In step ST2905, the eNB that has transmitted beam switching instruction information to the UE performs uplink scheduling in step ST3002 to cause the UE to transmit, using the target beam, the uplink data that was in HARQ processing in the source beam since the first transmission. At this time, the eNB may use the information regarding the uplink data that was in HARQ processing in the source beam and received in step ST3001. The notification may use the target beam.

[0836] In step ST3002, the UE that has received the scheduling information in the target beam for the first transmission of the uplink data transmits, according to the scheduling information, to the eNB, using the target beam, the first transmission of the uplink data that was in HARQ processing in the source beam.

[0837] By doing so, it becomes possible to communicate the uplink data that was in HARQ processing in the source beam, using the target beam, without having the UE transmit an SR in the target beam.

[0838] Since the UE does not need to transmit an SR, power consumption of the UE can be reduced. Also, it becomes possible to shorten the time from beam switching to transmission of the uplink data of the UE.

[0839] A specific example of a method for performing HARQ of the foregoing specific example (2) using the source beam and the target beam is disclosed. FIG. 33 is a diagram showing an example of a sequence regarding a method of performing retransmission of data during HARQ in a second modification of Embodiment 13 using the target beam. In FIG. 33, when transmitting uplink data using the target beam, a sequence of a method in which the UE does not need to transmit an SR is shown. Since the sequence shown in FIG. 33 is similar to the sequence shown in FIG. 32, the same step numbers are assigned to the same steps and common explanations are omitted. Here, mainly different parts will be described.

[0840] Disclose the downlink data. In step ST2901, the UE that fails to receive the downlink data from the eNB uses HARQ processing to send a Nack, which is delivery failure (delivery unsuccessful) information, to the eNB using the source beam in step ST3101.

[0841] In step ST2903, the eNB determines a beam switch for the UE.

[0842] In step ST3103, the eNB provides the undelivered downlink data information, which is information about the downlink data in HARQ processing in the source beam, to the target beam. If the source beam and the target beam are of the same eNB, it is performed within the same eNB. In this case, the information about the downlink data in HARQ processing may be applied from the source beam to the target beam.

[0843] The information about the downlink data in HARQ processing in the source beam may be any information that can identify the data to be transmitted in the target beam. Here, since the eNB has received a Nack from the UE, it may be information that can identify the data for retransmission.

[0844] In step ST2905, the eNB notifies the UE of the beam switch instruction information using the source beam.

[0845] The UE that has received the beam switch instruction information synchronizes with the target beam in step ST2906.

[0846] In step ST3105, the eNB performs downlink scheduling for retransmitting the downlink data that was in HARQ processing in the source beam using the target beam. At this time, the eNB may use the information about the downlink data in HARQ processing in the source beam received in step ST3103. The notification may use the target beam.

[0847] In step ST3105, the eNB that has notified the UE of the scheduling information for retransmission in the target beam for the first transmission of data transmits, according to the scheduling information, to the UE the retransmission data of the downlink data being processed by HARQ in the source beam using the target beam.

[0848] The UE that has received the downlink scheduling information in step ST3105 receives, according to the scheduling information, in step ST3106 the retransmission data of the downlink data being processed by HARQ in the source beam using the target beam.

[0849] By doing so, it becomes possible to communicate the downlink data being processed by HARQ in the source beam using the target beam.

[0850] In FIG. 33, the case where the eNB transmits the first retransmission data of the downlink data using the target beam is disclosed, but it is not limited to the first time. The same may be done for any number of times. When Nack continues in the source beam, the retransmission data at the time when the beam switching is executed is transmitted using the target beam.

[0851] The uplink data is disclosed. The eNB that has failed to receive the uplink data from the UE in step ST2902 transmits, by HARQ processing, to the UE in step ST3102 a Nack which is delivery failure (unsuccessful delivery) information. At this time, the uplink scheduling information for the retransmission data is notified.

[0852] In step ST2903, the eNB determines a beam switch for the UE.

[0853] In step ST2903, the eNB that has determined to switch the beam for the UE provides, in step ST3104, the outstanding uplink data information, which is information regarding the uplink data being processed in HARQ in the source beam, to the target beam. If the source beam and the target beam are of the same eNB, this is done within the same eNB. In this case, the information regarding the uplink data being processed in HARQ may be applied from the source beam to the target beam.

[0854] The information regarding the uplink data being processed in HARQ in the source beam may be any information that can identify the data to be transmitted in the target beam. Here, since a Nack is being sent to the UE, it is advisable to include information that can identify the scheduling information for the uplink retransmission data.

[0855] The UE that has received the beam switching instruction information from the eNB in step ST2905 retransmits the uplink data to the eNB using the target beam in step ST3107 according to the scheduling information for the uplink data retransmission received using the source beam in step ST3102.

[0856] The uplink scheduling information for the retransmission data that the eNB notifies the UE using the source beam in step ST3102 may be used as the uplink scheduling information for the retransmission data when using the target beam.

[0857] In the sequence shown in Figure 33, in step ST3102, the eNB sends a Nack to the UE using the source beam and notifies the uplink scheduling information for the retransmission data. As another method, the uplink scheduling information for the retransmission data may be notified using the target beam.

[0858] The eNB that has sent the beam switching instruction information to the UE in step ST2905 sends the uplink scheduling information for the retransmission data to the UE using the target beam in order to cause the retransmission data to be transmitted using the target beam.

[0859] At this time, the eNB may use the information on the uplink data being processed by HARQ in the source beam received in step ST3104.

[0860] The UE that has received the uplink scheduling information for the uplink retransmission data transmits, in step ST3107, to the eNB, according to the scheduling information, using the target beam, a retransmission of the uplink data being processed by HARQ in the source beam.

[0861] By doing so, when the reception quality of the source beam deteriorates, it becomes possible to communicate starting from the retransmission using the target beam.

[0862] Therefore, it becomes possible to improve the communication quality better and earlier compared to the method of communicating using the target beam from the first transmission.

[0863] Another method is disclosed. FIG. 34 is a diagram showing an example of a sequence regarding a method of performing from the delivery success (Ack) / delivery failure (Nack) of data being processed by HARQ in a modified example 2 of Embodiment 13 using a target beam. In FIG. 34, when transmitting uplink data using the target beam, a sequence of a method in which the UE does not need to transmit an SR is shown. Since the sequence shown in FIG. 34 is similar to the sequence shown in FIG. 33, the same step numbers are assigned to the same steps, and common explanations are omitted. Here, mainly different parts will be described.

[0864] Downlink data is disclosed. In step ST2901, the eNB transmits downlink data to the UE. Assume that the UE fails to receive this downlink data.

[0865] In step ST2903, the eNB determines beam switching for the UE. In step ST3201, the eNB provides the target beam with the undelivered downlink data information, which is information regarding the downlink data being processed by HARQ in the source beam. When the source beam and the target beam are of the same eNB, it is performed within the same eNB. In this case, the information regarding the downlink data being processed by HARQ may be applied from the source beam to the target beam.

[0866] The information regarding the downlink data being processed by HARQ in the source beam may be any information that can identify the data to be transmitted in the target beam. When a Nack is received from the UE later, it is preferably information that can identify the data for retransmission.

[0867] The UE that fails to receive the downlink data from the eNB in step ST2901 needs to send an Ack / Nack to the eNB at a predetermined timing through HARQ processing. Here, it is assumed that the UE receives beam switching instruction information from the eNB in step ST2905 before sending the Ack / Nack.

[0868] The UE that receives the beam switching instruction information in step ST2905 synchronizes with the target beam in step ST2906.

[0869] In step ST3203, the UE sends a Nack to the eNB using the target beam. If the downlink data is successfully received in step ST2901, an Ack is sent. Here, since the reception fails, that is, the delivery fails, a Nack is sent. The transmission timing of the Ack / Nack may be a predetermined timing determined by the reception timing of the downlink data in the source beam.

[0870] The eNB derives the timing at which an Ack / Nack is transmitted using the information on the downlink data in the source beam received in step ST3201 during HARQ processing. In step ST3203, the eNB receives a Nack from the UE at the derived timing.

[0871] The eNB that has received a Nack from the UE in step ST3203 performs, in step ST3204, downlink scheduling for the UE to retransmit the downlink data that was in HARQ processing in the source beam using the target beam. At this time, the eNB may use the information on the downlink data in the source beam received in step ST3201 during HARQ processing.

[0872] The eNB that has notified the UE of the scheduling information for retransmission in the target beam in step ST3204 transmits the retransmission data of the downlink data in the source beam in HARQ processing to the UE using the target beam according to the scheduling information.

[0873] The UE that has received the downlink scheduling information in step ST3204 receives, in step ST3205, the retransmission data of the downlink data in the source beam in HARQ processing using the target beam according to the scheduling information.

[0874] By doing so, it becomes possible to communicate the downlink data in HARQ processing in the source beam using the target beam.

[0875] The uplink data is disclosed. In step ST2902, the eNB fails to receive the uplink data from the UE.

[0876] In step ST2903, the eNB determines to switch the beam for the UE.

[0877] In step ST2903, the eNB that has determined to switch the beam for the UE provides, in step ST3202, the undelivered uplink data information, which is information on the uplink data being processed by HARQ in the source beam, to the target beam. When the source beam and the target beam are of the same eNB, this is done within the same eNB. In this case, the information on the uplink data being processed by HARQ may be applied from the source beam to the target beam.

[0878] The information on the uplink data being processed by HARQ in the source beam may be any information that can identify the data to be transmitted in the target beam. When sending a Nack to the UE later, it is advisable to use information that can identify the data for retransmission.

[0879] The eNB that has failed to receive the uplink data from the UE in step ST2902 needs to send an Ack / Nack to the UE at any timing through HARQ processing. Here, it is assumed that in step ST2905, the eNB has sent beam switching instruction information to the UE before sending the Ack / Nack.

[0880] The UE that has received the beam switching instruction information in step ST2905 performs synchronization with the target beam in step ST2906.

[0881] In step ST3206, the eNB sends a Nack to the UE using the target beam. If the uplink data was successfully received in step ST2902, an Ack is sent. Here, since the reception has failed, that is, the delivery has failed, a Nack is sent. The timing of sending the Ack / Nack may be any timing.

[0882] In step ST3206, the eNB transmits, to the UE, uplink scheduling information for causing the UE to transmit, using the target beam, the uplink data that was being processed by HARQ in the source beam, together with a Nack, for retransmission. At this time, the eNB may use the information regarding the uplink data that was being processed by HARQ in the source beam and received in step ST3202.

[0883] Although the disclosure has been made to transmit the uplink scheduling information together with a Nack, only the uplink scheduling information may be sufficient. The uplink scheduling information may also serve as a Nack. It is advisable to include information indicating that this is a retransmission in the scheduling information.

[0884] In step ST2905, the UE that has received the beam switching instruction information from the eNB performs, in step ST3207, retransmission of uplink data to the eNB using the target beam, in accordance with the scheduling information for uplink data retransmission received using the target beam in step ST3206.

[0885] By doing so, when the reception quality of the source beam deteriorates, it becomes possible to communicate starting from the transmission of an Ack / Nack using the target beam.

[0886] Therefore, it becomes possible to improve the communication quality even earlier compared to the method of communicating using the target beam from the initial transmission.

[0887] By using the method disclosed in this modification example, it becomes possible to transmit the data that was not successfully delivered using the source beam, using the target beam.

[0888] By appropriately combining the methods disclosed above, it becomes possible to perform operations from the initial transmission, retransmission, or transmission of an Ack / Nack using the target beam.

[0889] By appropriately combining these methods according to the determination timing of beam switching, it becomes possible to perform beam switching at an optimal timing according to the radio wave environment or the like.

[0890] Therefore, even in a situation where beam switching frequently occurs, it becomes possible to perform switching to a more optimal beam at an appropriate timing, and it becomes possible to reduce deterioration of communication quality and delays and interruptions in communication due to switching failures.

[0891] In Modification 2 from Embodiment 12 to Embodiment 13, beam switching was disclosed. As beam switching, for beam switching between beams within the same cell, beam switching between beams of different cells, or beam switching between beams of different eNBs, the methods disclosed in the above-described embodiments may be appropriately combined and applied. Thereby, it becomes possible to reduce deterioration of communication quality due to beam switching processing and delays and interruptions in communication due to switching failures.

[0892] Each of the above-described embodiments and its 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 components of each embodiment and its modifications can be appropriately changed or omitted.

[0893] 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. An infinite number of modifications not illustrated can be considered without departing from the scope of the present invention.

Description of Reference Numerals

[0894] 901,903 MeNB, 902,904 SeNB, 905,906,2402 UE, 907,909,912,914 MAC, 908,910,913,915 RLC, 911,916 PDCP, 2401 Multi-element antenna, 2403,2404,2405 Coverage.

Claims

1. A user device; A communication system comprising: a base station that communicates with the user device by switching among a plurality of beams that can be formed by beamforming; When the user equipment moves from a first coverage of a first beam transmitted by the base station to a second coverage of a second beam transmitted by the base station and from a first cell to a second cell, Receive a Cell Radio Network Temporary Identifier (C-RNTI) from the base station; synchronizing the user device with the first beam and the second beam using a synchronization signal; switching from the first beam to the second beam using a beam identifier; receiving, in the second cell, from the base station, scheduling information transmitted using the second beam; Obtaining the scheduling information using the C-RNTI; Communication systems.

2. A base station that communicates with a user device by switching between a plurality of beams that can be formed by beamforming, When the user equipment moves from a first coverage of a first beam transmitted by the base station to a second coverage of a second beam transmitted by the base station and from a first cell to a second cell, Transmitting a Cell Radio Network Temporary Identifier (C-RNTI) to the user equipment; transmitting a synchronization signal to the user device for synchronizing the user device with the first beam and the second beam; assigning beam identifiers to the first beam and the second beam for use by the user equipment to switch from the first beam to the second beam; transmitting, to the user equipment, scheduling information used in the second cell, using the second beam, the scheduling information being acquired by the user equipment using the C-RNTI; Base station.

3. A user device that communicates with a base station, the base station communicating with the user device by switching between a plurality of beams that can be formed by beamforming, the user device comprising: When moving from a first coverage of a first beam transmitted by the base station to a second coverage of a second beam transmitted by the base station and from a first cell to a second cell, Receive a Cell Radio Network Temporary Identifier (C-RNTI) from the base station; synchronizing the user device with the first beam and the second beam using a synchronization signal; switching from the first beam to the second beam using a beam identifier; receiving, in the second cell, from the base station, scheduling information transmitted using the second beam; Obtaining the scheduling information using the C-RNTI; User equipment.

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