JP6140323B2 - Mobile communication system, base station and method - Google Patents

Description

  The present invention relates to a mobile communication system in which a new carrier structure is introduced.

  In 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, the introduction of a new carrier structure (NCT: New Carrier Type) is being considered after Release 12.

  As one of NCTs, it has been proposed to reduce a cell-specific reference signal (CRS) as compared with a conventional carrier structure (LCT: Legacy Carrier Type) (for example, see Non-Patent Document 1). As a result, the radio resource used for CRS transmission can be diverted to transmission of user data (data signal) and the like, thereby improving throughput.

3GPP contribution "R1-113289"

  However, although the above-described CRS reduction technology related to NCT can improve throughput, there is room for improvement in terms of reducing power consumption (that is, power saving).

  Therefore, the present invention provides a mobile communication system, a base station, and a user terminal that can realize efficient power saving.

  The mobile communication system according to the first feature includes a base station that manages cells. The base station includes a transmission unit that transmits a radio signal to user terminals in the cell, and a base station side control unit that sets a transmission stop period for stopping the operation of the transmission unit. The transmitter intermittently transmits a cell-specific reference signal that is a kind of the radio signal. The base station side control unit sets the transmission stop period in a period in which the transmission unit does not transmit the cell-specific reference signal.

  The base station according to the second feature manages cells. The base station includes a transmission unit that transmits a radio signal to user terminals in the cell, and a base station side control unit that sets a transmission stop period for stopping the operation of the transmission unit. The transmitter intermittently transmits a cell-specific reference signal that is a kind of the radio signal. The base station side control unit sets the transmission stop period in a period in which the transmission unit does not transmit the cell-specific reference signal.

  The user terminal which concerns on the 3rd characteristic performs the intermittent reception which receives the radio signal from a base station intermittently. When the user terminal is notified from the base station of a reception unit that is switched from a stop state to an operation state at a start timing according to a predetermined cycle, and a transmission stop period in which transmission of the radio signal is stopped, the transmission is performed. A terminal-side control unit that adjusts the activation timing so as to avoid the stop period.

  The user terminal which concerns on a 4th characteristic performs the intermittent reception which receives the radio signal from a base station intermittently. When the user terminal is notified from the base station of a receiving unit that is switched from a stopped state to an operating state at a start timing according to a predetermined cycle, and a transmission timing of a control signal by an extended physical downlink control channel, the user terminal A terminal-side control unit that adjusts the activation timing so that the reception unit receives the control signal at a signal transmission timing.

  ADVANTAGE OF THE INVENTION According to this invention, the mobile communication system, base station, and user terminal which can implement | achieve the efficient power saving of a base station can be provided.

It is a block diagram of the LTE system which concerns on 1st Embodiment thru | or 3rd Embodiment. It is a block diagram of UE which concerns on 1st Embodiment thru | or 3rd Embodiment. It is a block diagram of eNB which concerns on 1st Embodiment thru | or 3rd Embodiment. It is a protocol stack figure of the radio | wireless interface in a LTE system. It is a block diagram of the radio | wireless frame used with a LTE system. It is a figure for demonstrating NCT which concerns on 1st Embodiment thru | or 3rd Embodiment compared with LCT. It is a figure which shows the operating environment which concerns on 1st Embodiment thru | or 3rd Embodiment. It is a figure for demonstrating the setting method 1 of the DTX area which concerns on 1st Embodiment. It is a figure for demonstrating the notification method of the DTX area which concerns on 1st Embodiment. It is a figure for demonstrating DRX operation | movement. It is a figure for demonstrating operation | movement of UE which concerns on 2nd Embodiment. It is a figure for demonstrating operation | movement of UE which concerns on 3rd Embodiment. It is a figure for demonstrating operation | movement of UE which concerns on 3rd Embodiment.

[Outline of Embodiment]
The mobile communication system according to the first to third embodiments includes a base station that manages cells. The base station includes a transmission unit that transmits a radio signal to user terminals in the cell, and a base station side control unit that sets a transmission stop period for stopping the operation of the transmission unit. The transmitter intermittently transmits a cell-specific reference signal that is a kind of the radio signal. The base station side control unit sets the transmission stop period in a period in which the transmission unit does not transmit the cell-specific reference signal.

  In the first to third embodiments, the transmission stop period can be changed dynamically. The said transmission part transmits the control signal which is a kind of said radio signal to the said user terminal by the extended physical downlink control channel allocated to each said user terminal. The base station side control unit controls allocation of the extended physical downlink control channel so as to expand the transmission stop period.

  In the first to third embodiments, the transmission stop period can be changed dynamically. The said transmission part transmits the data signal which is a kind of said radio signal to the said user terminal by the physical downlink shared channel allocated to the said user terminal separately. The base station side control unit controls allocation of the physical downlink shared channel so as to expand the transmission stop period.

  Or in 1st Embodiment thru | or 3rd Embodiment, the said transmission stop area is presetly set. The said transmission part transmits the control signal which is a kind of said radio signal to the said user terminal by the extended physical downlink control channel allocated to each said user terminal. The base station side control unit controls allocation of the extended physical downlink control channel so as to avoid the transmission stop period.

  In the first to third embodiments, the transmission stop period is fixedly set in advance. The said transmission part transmits the data signal which is a kind of said radio signal to the said user terminal by the physical downlink shared channel allocated to the said user terminal separately. The base station side control unit controls allocation of the physical downlink shared channel so as to avoid the transmission stop period.

  In 1st Embodiment thru | or 3rd Embodiment, the said base station side control part notifies the said transmission stop area to the said user terminal by broadcast or unicast.

  In 1st Embodiment thru | or 3rd Embodiment, the said base station side control part notifies the said transmission stop area to an adjacent base station.

  In 2nd Embodiment, the said user terminal controls the intermittent reception which receives the said radio signal intermittently based on the receiving part which receives the said radio signal, and the said transmission stop area notified from the said base station A terminal-side control unit. The receiving unit is switched from a stopped state to an operating state at a start timing according to a predetermined cycle. The terminal-side control unit adjusts the activation timing so as to avoid the transmission stop period.

  In 3rd Embodiment, the said user terminal is provided with the receiving part which receives the said radio signal, and the terminal side control part which controls the intermittent reception which receives the said radio signal intermittently. The receiving unit is switched from a stopped state to an operating state at a start timing according to a predetermined cycle. When the terminal-side control unit is notified of the transmission timing of the control signal by the extended physical downlink control channel from the base station, the reception unit receives the control signal at the transmission timing of the control signal. Adjust the startup timing.

The base station according to the first to third embodiments manages a cell. The base station includes a transmission unit that transmits a radio signal to user terminals in the cell, and a base station side control unit that sets a transmission stop period for stopping the operation of the transmission unit. The transmitter intermittently transmits a cell-specific reference signal that is a kind of the radio signal. The base station side control unit sets the transmission stop period in a period in which the transmission unit does not transmit the cell-specific reference signal.

  The user terminal which concerns on 2nd Embodiment performs the intermittent reception which receives the radio signal from a base station intermittently. When the user terminal is notified from the base station of a reception unit that is switched from a stop state to an operation state at a start timing according to a predetermined cycle, and a transmission stop period in which transmission of the radio signal is stopped, the transmission is performed. A terminal-side control unit that adjusts the activation timing so as to avoid the stop period.

  The user terminal which concerns on 3rd Embodiment performs the intermittent reception which receives the radio signal from a base station intermittently. When the user terminal is notified from the base station of a receiving unit that is switched from a stopped state to an operating state at a start timing according to a predetermined cycle, and a transmission timing of a control signal by an extended physical downlink control channel, the user terminal A terminal-side control unit that adjusts the activation timing so that the reception unit receives the control signal at a signal transmission timing.

[First Embodiment]
Hereinafter, an embodiment in which the present invention is applied to LTE (Long Term Evolution) standardized by 3GPP will be described with reference to the drawings.

(Configuration of LTE system)
FIG. 1 is a configuration diagram of an LTE system according to the first embodiment. As shown in FIG. 1, the LTE system includes a plurality of UEs (User Equipment) 100, an E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) 10, and an EPC (Evolved Packet Core) 20. The E-UTRAN 10 corresponds to a radio access network, and the EPC 20 corresponds to a core network. The E-UTRAN 10 and the EPC 20 constitute an LTE system network.

  The UE 100 is a mobile communication device, and performs wireless communication with a connection destination cell (serving cell). UE100 is corresponded to a user terminal.

  The E-UTRAN 10 includes a plurality of eNBs 200 (evolved Node-B). The eNB 200 corresponds to a base station. The eNB 200 manages one or a plurality of cells, and performs radio communication with the UE 100 that has established a connection with the own cell. Note that “cell” is used as a term indicating a minimum unit of a radio communication area, and is also used as a term indicating a function of performing radio communication with the UE 100.

  The eNB 200 has, for example, a radio resource management (RRM) function, a user data routing function, and a measurement control function for mobility control and scheduling.

  The EPC 20 includes a plurality of MME (Mobility Management Entity) / S-GW (Serving-Gateway) 300. The MME is a network node that performs various types of mobility control for the UE 100, and corresponds to a control station. The S-GW is a network node that performs transfer control of user data, and corresponds to an exchange.

  The eNB 200 is connected to each other via the X2 interface. Moreover, eNB200 is connected with MME / S-GW300 via S1 interface.

  Next, configurations of the UE 100 and the eNB 200 will be described.

  FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100 includes a plurality of antennas 101, a radio transceiver 110, a user interface 120, a GNSS (Global Navigation Satellite System) receiver 130, a battery 140, a memory 150, a processor 160, Have. The memory 150 and the processor 160 constitute a terminal side control unit. The UE 100 may not have the GNSS receiver 130. Further, the memory 150 may be integrated with the processor 160, and this set (that is, a chip set) may be used as the processor 160 '.

  The plurality of antennas 101 and the wireless transceiver 110 are used for transmitting and receiving wireless signals. Radio transceiver 110 includes a transmission unit 111 that converts a baseband signal (transmission signal) output from processor 160 into a radio signal and transmits the radio signal from a plurality of antennas 101. The radio transceiver 110 includes a reception unit 112 that converts radio signals received by the plurality of antennas 101 into baseband signals (reception signals) and outputs the baseband signals to the processor 160.

  The user interface 120 is an interface with a user who owns the UE 100, and includes, for example, a display, a microphone, a speaker, and various buttons. The user interface 120 receives an operation from the user and outputs a signal indicating the content of the operation to the processor 160. The GNSS receiver 130 receives a GNSS signal and outputs the received signal to the processor 160 in order to obtain location information indicating the geographical location of the UE 100. The battery 140 stores power to be supplied to each block of the UE 100.

  The memory 150 stores a program executed by the processor 160 and information used for processing by the processor 160.

  The processor 160 performs signal processing such as modulation / demodulation and encoding / decoding of the baseband signal. In addition, the processor 160 executes various programs by executing programs stored in the memory 150. Further, the processor 160 executes various controls and various communication protocols described later. The processor 160 may include a codec that performs encoding / decoding of an audio / video signal.

  FIG. 3 is a block diagram of the eNB 200. As illustrated in FIG. 3, the eNB 200 includes a plurality of antennas 201, a radio transceiver 210, a network interface 220, a memory 230, and a processor 240. The memory 230 and the processor 240 constitute a base station side control unit.

  The plurality of antennas 201 and the wireless transceiver 210 are used for transmitting and receiving wireless signals. The radio transceiver 210 includes a transmission unit 211 that converts a baseband signal (transmission signal) output from the processor 240 into a radio signal and transmits the radio signal from the plurality of antennas 201. The radio transceiver 210 includes a reception unit 212 that converts radio signals received by the plurality of antennas 201 into baseband signals (reception signals) and outputs the baseband signals to the processor 240.

  The network interface 220 is connected to the neighboring eNB 200 via the X2 interface and is connected to the MME / S-GW 300 via the S1 interface. The network interface 220 is used for communication performed on the X2 interface and communication performed on the S1 interface.

  The memory 230 stores a program executed by the processor 240 and information used for processing by the processor 240.

  The processor 240 performs signal processing such as modulation / demodulation and encoding / decoding of the baseband signal. In addition, the processor 240 executes programs stored in the memory 230 to perform various controls. Further, the processor 240 executes various controls and various communication protocols described later.

  FIG. 4 is a protocol stack diagram of a radio interface in the LTE system. As shown in FIG. 4, the radio interface protocol is divided into layers 1 to 3 of the OSI reference model, and layer 1 is a physical (PHY) layer. Layer 2 includes a MAC (Media Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Convergence Protocol) layer. Layer 3 includes an RRC (Radio Resource Control) layer.

  The physical layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data is transmitted between the physical layer of the UE 100 and the physical layer of the eNB 200 via a physical channel.

  The MAC layer performs data priority control, retransmission processing by hybrid ARQ (HARQ), and the like. Data is transmitted via the transport channel between the MAC layer of the UE 100 and the MAC layer of the eNB 200. The MAC layer of the eNB 200 includes a scheduler that determines uplink / downlink transport formats (transport block size, modulation / coding scheme (MCS)) and allocated resource blocks.

  The RLC layer transmits data to the RLC layer on the receiving side using functions of the MAC layer and the physical layer. Data is transmitted between the RLC layer of the UE 100 and the RLC layer of the eNB 200 via a logical channel.

  The PDCP layer performs header compression / decompression and encryption / decryption.

  The RRC layer is defined only in the control plane. Control messages (RRC messages) for various settings are transmitted between the RRC layer of the UE 100 and the RRC layer of the eNB 200. The RRC layer controls the logical channel, the transport channel, and the physical channel according to establishment, re-establishment, and release of the radio bearer. If there is an RRC connection between the RRC of the UE 100 and the RRC of the eNB 200, the UE 100 is in a connected state (RRC connected state), and otherwise, the UE 100 is in an idle state (RRC idle state).

  A NAS (Non-Access Stratum) layer located above the RRC layer performs session management, mobility management, and the like.

  FIG. 5 is a configuration diagram of a radio frame used in the LTE system. In the LTE system, OFDMA (Orthogonal Frequency Division Multiplexing Access) is applied to the downlink and SC-FDMA (Single Carrier Frequency Multiple Access) is applied to the uplink.

  As shown in FIG. 5, the radio frame is composed of 10 subframes arranged in the time direction, and each subframe is composed of two slots arranged in the time direction. The length of each subframe is 1 ms, and the length of each slot is 0.5 ms. Each subframe includes a plurality of resource blocks (RB) in the frequency direction and includes a plurality of symbols in the time direction. The resource block includes a plurality of subcarriers in the frequency direction. A radio resource unit configured by one subcarrier and one symbol is referred to as a resource element (RE).

  Among radio resources allocated to the UE 100, a frequency resource can be specified by a resource block, and a time resource can be specified by a subframe (or slot).

(NCT)
The LTE system according to the first embodiment supports NCT (New Carrier Type) in the downlink. NCT is scheduled to be introduced after release 12, and a new carrier structure that is not restricted by the carrier structure in the previous releases (that is, release 8 to release 11) is adopted.

  FIG. 6 is a diagram for explaining NCT in comparison with a conventional carrier structure (LCT: Legacy Carrier Type).

  As shown in FIG. 6, in LCT, the interval of the first few symbols of each subframe is a control region mainly used as a physical downlink control channel (PDCCH) for transmitting a control signal. Further, the remaining section of each subframe is a data area mainly used as a physical downlink shared channel (PDSCH) for transmitting user data (data signal).

  The PDCCH transmits a control signal. The control signal includes, for example, uplink SI (Scheduling Information), downlink SI, and TPC bits. The uplink SI is information indicating allocation of uplink radio resources, and the downlink SI is information indicating allocation of downlink radio resources. The TPC bit is information instructing increase / decrease in uplink transmission power. These pieces of information are referred to as downlink control information (DCI).

  The PDSCH transmits a control signal and / or a data signal. For example, the downlink data area may be allocated only to the data signal, or may be allocated so that the data signal and the control signal are multiplexed.

  In each subframe, a cell-specific reference signal (CRS) and a channel state information reference signal (CSI-RS) are provided in a distributed manner. Each of CRS and CSI-RS is configured by a predetermined orthogonal signal sequence. In LCT, the CRS is provided in all subframes in the time axis direction. The CRS is a signal used by the UE 100 for downlink channel state measurement and received power (RSRP: Reference Signal Received Power) measurement.

  On the other hand, in NCT, an extended physical downlink control channel (ePDCCH) is provided as a physical channel for transmitting a control signal, instead of PDCCH. The ePDCCH is a physical channel that transmits a control signal in the data region (PDSCH region). The ePDCCH is allocated to each UE 100, and a control signal can be transmitted to each UE 100. In NCT, the CRS is provided only in some subframes in the time axis direction.

  In carrier aggregation, the primary component carrier (PCC) may be LCT, and NCT may be applied only to the secondary component carrier (SCC).

(Operation according to the first embodiment)
(1) Outline of Operation First, an outline of operation according to the first embodiment will be described. FIG. 7 is a diagram illustrating an operating environment according to the first embodiment. As shown in FIG. 7, a plurality of UEs 100 (UEs 100-1 to 100-n
) Is located in a cell managed by the eNB 200. In addition, NCT with reduced CRS is introduced into a cell managed by the eNB 200.

  eNB200 has the transmission part 211 (refer FIG. 3) which transmits a radio signal with respect to UE100 in a cell. The radio signal transmitted by the transmission unit 211 is the above-described control signal, data signal, reference signal (CRS, CSI-RS), or the like. The transmission unit 211 includes a power amplifier, and is a portion with high power consumption in the eNB 200.

  Moreover, eNB200 has the processor 240 (refer FIG. 3) which sets the transmission stop (DTX: DiscontinuousTransmission) section which stops operation | movement of the transmission part 211. FIG. For example, the processor 240 stops power supply to the transmission unit 211 (power amplifier) and stops the operation of the transmission unit 211. By stopping the operation of the transmission unit 211, power consumption reduction (power saving) of the eNB 200 is realized.

  Note that the processor 240 stops the operation of the transmission unit 211 in the DTX period, but does not stop the operation of the reception unit 212. Therefore, reception of radio signals from the UE 100 can be continued even in the DTX section.

  The transmission part 211 transmits CRS intermittently. As described above, the transmission unit 211 transmits CRS only in some subframes without transmitting CRS in all subframes.

  The processor 240 sets a DTX interval in a period (subframe) in which the transmission unit 211 does not transmit CRS. That is, the operation of the transmission unit 211 is stopped in the subframe in which the transmission unit 211 does not transmit CRS.

  In this way, by setting the DTX interval in a period in which the CRS is not transmitted by the transmission unit 211, power saving of the eNB 200 can be realized while enabling channel state measurement, RSRP measurement, and the like.

(2) DTX section setting method 1
FIG. 8 is a diagram for explaining the setting method 1 of the DTX section. In setting method 1, the DTX section can be dynamically changed.

  As illustrated in FIG. 8, the eNB 200 transmits a CRS at a rate of once every 5 subframes. Specifically, the CRS is transmitted in n subframes, (n + 5) subframes, (n + 10) subframes, and (n + 15) subframes.

  Moreover, eNB200 sets a DTX area in the period when the transmission part 211 does not transmit CRS. In the example of FIG. 8, (n + 2) to (n + 3) subframes, (n + 8) subframes, and (n + 12) to (n + 14) subframes are set as the DTX section.

  In setting method 1, eNB 200 controls allocation of ePDCCH so as to expand the DTX section. Since the ePDCCH can be allocated to each UE 100, for example, by adjusting the ePDCCH transmission to be concentrated in time for a plurality of UEs 100 (UEs 100-1 to 100-n), the DTX period can be expanded. In the example of FIG. 8, the UE 100-1 is assigned ePDCCH in a subframe in which CRS is transmitted. The UE 100-1 is assigned ePDCCH in the subframe next to the subframe in which the CRS is transmitted.

  eNB200 sets the allocation subframe (and allocation resource block) of ePDCCH for every UE100. And eNB200 transmits a control signal in the allocation sub-frame (and allocation resource block) of ePDCCH. Therefore, eNB200 can expand a DTX section by adjusting the setting of an allocation subframe or adjusting the presence or absence of transmission of a control signal.

  Moreover, in the setting method 1, eNB200 controls allocation of PDSCH so that a DTX area may be expanded. Since the PDSCH can be individually assigned to the UE 100, for example, by adjusting the PDSCH transmission to be concentrated in time for a plurality of UEs 100 (UEs 100-1 to 100-n), the DTX period can be expanded.

  Note that the eNB 200 may determine the degree of adjustment for each of the plurality of UEs 100 in consideration of a traffic situation or a data type (QoS or the like).

  Further, in the setting method 1, the eNB 200 may expand the DTX section by adjusting the transmission of ACK / NACK for data received from the UE 100. For example, the eNB 200 transmits ACK / NACK from the PCC when the NCT is SCC. In addition, when the timing at which the specified time (8 subframes) for ACK / NACK transmission has elapsed after receiving data from the UE 100, the eNB 200, after the elapse of the specified time (in the DTX interval) ACK / NACK is transmitted after elapse).

(3) DTX section setting method 2
In the setting method 1, the DTX interval can be dynamically changed. In the setting method 2, the DTX interval is fixedly set in advance.

  Although the setting method 1 can further reduce the power consumption of the eNB 200 by expanding the DTX section, the scheduling load of the eNB 200 is large. In setting method 2, since the DTX interval is fixedly set in advance, the scheduling load of eNB 200 is smaller than that in setting method 1.

  In the setting method 2, the eNB 200 controls ePDCCH allocation so as to avoid a DTX interval that is fixedly set in advance. Moreover, eNB200 controls allocation of PDSCH so that the DTX area fixedly set beforehand may be avoided. Other controls are the same as in setting method 1.

(4) Notification of DTX section to UE The information on the DTX section needs to be shared with the UE 100 in order for the UE 100 to appropriately perform channel state measurement and the like. Further, when the UE 100 is performing a DRX (Discontinuous Reception) operation, the UE 100 can improve the efficiency of the DRX operation by considering the DTX interval (details will be described in the second embodiment).

  Therefore, in the first embodiment, the eNB 200 notifies the UE 100 of the DTX section by broadcast or unicast.

  As a notification method by broadcast, the eNB 200 includes information indicating the DTX section in the master information block (MIB) or the system information block (SIB) and transmits the information to the UE 100.

  Here, the information indicating the DTX interval is a subframe number corresponding to the DTX interval in the setting method 1 described above. On the other hand, in the setting method 2 described above, the information indicating the DTX section may be a subframe number corresponding to the DTX section, or may be pattern information of the DTX section. For example, as illustrated in FIG. 9, when the eNB 200 activates the transmission unit 211 at a certain activation cycle (dtxCycle) and continues the operation state for a certain activation time (dtx-onDuration), the activation cycle and the activation time are illustrated. May be information indicating a DTX section.

  As a notification method by unicast, the eNB 200 includes information indicating a DTX section in the RRC message and transmits the information to the UE 100. Alternatively, as a notification method by unicast, the eNB 200 transmits to the UE 100 the MBSFN (MBMS Single Frequency Network) subframe notification message including the DTX flag. In this case, when the DTX flag is ON, the MBSFN subframe is read as a DTX section.

(5) Notification of DTX section to neighboring eNB Information of DTX section needs to be shared with neighboring eNB 200 in order for neighboring eNB 200 to appropriately perform mobility control of UE 100 under its control.

  In the first embodiment, the eNB 200 notifies the neighboring eNB 200 of the DTX interval. For example, the eNB 200 includes information indicating the DTX section in the X2 message and transmits the information to the neighboring eNB 200.

  Alternatively, an X2 message related to ABS (Almost Blank Subframe) is used, and a subframe corresponding to the DTX section is notified as ABS. Further, a DTX flag may be added to the ABS-related X2 message to indicate that the ABS is a complete non-transmitted subframe.

[Second Embodiment]
The second embodiment will be described mainly with respect to differences from the first embodiment. 2nd Embodiment is embodiment regarding DRX operation | movement of UE100.

  The UE 100 performs DRX operation (intermittent reception) in the connected state in order to save battery power. FIG. 10 is a diagram for explaining the DRX operation.

  As shown in FIG. 10, the processor 160 (see FIG. 2) of the UE 100 controls the DRX operation for intermittently receiving radio signals. Specifically, the reception unit 112 is activated at a constant activation cycle (drxCycle), and the operation state is continuously monitored for a certain activation time (drx-onDuration) to monitor the control signal. The activation cycle (drxCycle) is called a DRX cycle, and two types of long DRX cycle and short DRX cycle are defined. Thus, the receiving unit 112 is switched from the stopped state to the operating state at the start timing according to the DRX cycle (predetermined period).

  In the second embodiment, the processor 160 controls the DRX operation based on the DTX interval notified from the eNB 200. Specifically, the processor 160 adjusts the activation timing so as to avoid the DTX interval.

  FIG. 11 is a diagram for explaining the operation of the UE 100 according to the second embodiment. Here, a case is shown in which the DTX section is fixedly set in advance.

  As illustrated in FIG. 11, the processor 160 activates the reception unit 112 at the activation timing according to the DRX cycle. Further, as described in the first embodiment, the eNB 200 notifies the UE 100 of the DTX interval, and the processor 160 grasps the DTX interval.

  If the reception unit 112 is activated in the DTX section, the reception unit 112 is activated in vain. Therefore, the processor 160 adjusts the activation timing so as to avoid the DTX interval. Specifically, when the activation timing according to the DRX cycle overlaps with the DTX interval, the activation timing is advanced or sent so that the activation timing does not overlap with the DTX interval. In addition, you may adjust according to the kind of DRX cycle, such as delaying in the case of a long DRX cycle, and early in the case of a short DRX cycle.

  Thus, according to the second embodiment, it is possible to prevent the reception unit 112 from being activated unnecessarily, and to efficiently reduce the power consumption of the UE 100.

[Third Embodiment]
In the third embodiment, differences from the first embodiment and the second embodiment will be mainly described. The third embodiment is an embodiment obtained by partially changing the second embodiment.

  12 and 13 are diagrams for explaining the operation of the UE 100 according to the third embodiment.

  As shown in FIG. 12, ePDCCH is periodically allocated to UE 100 in NCT. Here, when the receiving unit 112 of the UE 100 is in a stopped state in the subframe in which the ePDCCH is set, the UE 100 cannot receive the control signal. On the other hand, when the receiving unit 112 of the UE 100 is in an operating state in a subframe in which ePDCCH is not set, control signal monitoring is wasted.

  As described above, the processor 160 of the UE 100 activates the reception unit 112 at the activation timing according to the DRX cycle. Also, the eNB 200 notifies the UE 100 of a subframe for setting ePDCCH (hereinafter referred to as “ePDCCH timing”), and the processor 160 knows the ePDCCH timing.

  As illustrated in FIG. 13, the processor 160 adjusts the activation timing of the reception unit 112 so that the reception unit 112 is in an operating state at the ePDCCH timing. Thereby, the receiving part 112 can receive a control signal at the transmission timing of the control signal by ePDCCH. Specifically, if the activation timing according to the DRX cycle does not overlap with the ePDCCH timing, the processor 160 makes the activation timing overlap with the ePDCCH timing by advancing or delaying the activation timing. Alternatively, the DRX cycle itself may be changed.

  In addition, you may adjust according to the kind of DRX cycle, such as delaying in the case of a long DRX cycle, and early in the case of a short DRX cycle. Alternatively, shortening (acceleration) / extension (delaying) may be switched according to the remaining battery level or QoS.

  Moreover, when eNB200 is setting the DTX area fixedly (in the case of the setting method 2), a DTX area and ePDCCH timing may overlap. In that case, the processor 160 may adjust the activation timing until the ePDCCH timing that does not overlap with the DTX interval.

  As described above, according to the third embodiment, it is possible to prevent the reception unit 112 from being activated unnecessarily, and to efficiently reduce the power consumption of the UE 100.

[Other Embodiments]
In the above-described embodiment, the case where the present invention is applied to the LTE system is mainly described. However, the present invention is not limited to the LTE system, and the present invention may be applied to a system other than the LTE system.

  E-UTRAN10, EPC20, UE100, antenna 101, radio transceiver 110, transmitter 111, receiver 112, user interface 120, GNSS receiver 130, battery 140, memory 150, processor 160, eNB200, antenna 201, radio transceiver 210, transmission unit 211, reception unit 212, network interface 220, memory 230, processor 240

Claims (5)

A mobile communication system having a base station for managing a cell,
The base station
A controller that performs an on / off operation to switch downlink transmission of the cell between on and off ;
In the case of performing the on / off operation, the control unit performs a process of periodically transmitting a radio signal including a cell-specific reference signal used for at least downlink received power measurement ,
The control unit performs a process of unicasting an RRC message including information indicating a transmission duration of the radio signal and information for the radio terminal to specify a period for receiving the radio signal by unicast. A mobile communication system. The mobile communication system according to claim 1, wherein the control unit further performs a process of notifying an adjacent base station of information indicating the transmission duration. 2. The mobile communication system according to claim 1, wherein the control unit further performs a process of notifying an adjacent base station of information for specifying a period at which the radio signal is received by the radio terminal. A base station managing a cell,
A controller that performs an on / off operation to switch downlink transmission of the cell between on and off;
In the case of performing the on / off operation, the control unit performs a process of periodically transmitting a radio signal including a cell-specific reference signal used for at least downlink received power measurement,
The control unit performs a process of unicasting an RRC message including information indicating a transmission duration of the radio signal and information for the radio terminal to specify a period for receiving the radio signal by unicast. A base station characterized by that. A method in a base station for managing a cell, comprising:
Performing an on / off operation to switch downlink transmission of the cell between on and off;
When performing the on / off operation, periodically transmitting a radio signal including at least a cell-specific reference signal used for downlink received power measurement;
Unicasting to the radio terminal an RRC message including information indicating the transmission duration of the radio signal and information for the radio terminal to specify a period for receiving the radio signal. And how to.

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