JP2015035688A - Base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize power-saving of a base station while preventing degradation of communication quality.SOLUTION: A large cell managed by a large cell base station MeNB200A has an area overlapped with a small cell managed by a small cell base station PeNB200B. The large cell base station MeNB200A is configured to manage the small cell base station PeNB200B via an X2 interface. When a load of the small cell base station PeNB200B is smaller than a threshold, the large cell base station MeNB200A transmits a setting request for a power-saving mode for reducing power consumption, to the small cell base station PeNB200B (S102). After handing over user terminals UE100-1 and UE100-2 in the small cell to the large cell or a neighboring small cell (S103 and S109), the small cell base station PeNB200B shifts into the power-saving mode (S111).

Description

  The present invention relates to a base station used in a mobile communication system.

  In 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, an energy saving technique for reducing power consumption of a base station is introduced (for example, see Non-Patent Document 1). For example, the power consumption of the base station can be reduced by stopping the operation of the cell managed by the base station at night when communication traffic is low.

3GPP Technical Report “TR 36.927 V11.0.0” September 2012

  However, by stopping the operation of the cell managed by the base station, the power consumption of the base station can be reduced, but the user terminal that has established a connection with the cell cannot communicate. Therefore, it is required to realize power saving of the base station while suppressing a decrease in communication quality of the entire network.

  Accordingly, an object of the present invention is to make it possible to realize power saving of a base station while suppressing a decrease in communication quality.

  The base station which concerns on one Embodiment is a base station which manages a cell. The base station includes a transmission unit that transmits a setting request for a power saving mode for reducing power consumption. The transmission unit transmits the setting request to a small cell base station that is installed in the cell and manages a small cell smaller than the cell.

  According to the base station according to the present invention, it is possible to realize power saving of the base station while suppressing a decrease in communication quality.

FIG. 1 is a configuration diagram of an LTE system. FIG. 2 is a block diagram of the UE. FIG. 3 is a block diagram of the eNB. FIG. 4 is a protocol stack diagram of a radio interface in the LTE system. FIG. 5 is a configuration diagram of a radio frame used in the LTE system. FIG. 6 is an explanatory diagram for explaining an operating environment of the mobile communication system according to the first embodiment. FIG. 7 is a diagram for explaining intermittent transmission according to the embodiment. FIG. 8 is a diagram for explaining the reduction of the number of transmission antennas according to the embodiment. FIG. 9 is a sequence diagram illustrating an example of the operation of the mobile communication system according to the first embodiment. FIG. 10 is an explanatory diagram for explaining the operating environment of the mobile communication system according to the second embodiment. FIG. 11 is a sequence diagram illustrating an example of the operation of the mobile communication system according to the second embodiment. FIG. 12 is a sequence diagram illustrating an example of the operation of the mobile communication system according to the modified example of the second embodiment.

  The base station (MeNB 200A) according to the present embodiment is a base station that manages cells. The base station includes a transmission unit that transmits a setting request for a power saving mode for reducing power consumption. The transmission unit transmits the setting request to a small cell base station that is installed in the cell and manages a small cell smaller than the cell.

  In 1st Embodiment, the said transmission part transmits the said setting request | requirement with respect to the said small cell base station, when the load of the said base station is lower than a threshold value.

  The base station according to the second embodiment is installed in the cell and indicates a load of the adjacent small cell base station from an adjacent small cell base station that is adjacent to the small cell and manages an adjacent small cell smaller than the cell. A receiving unit that receives the load information is further provided. The transmission unit transmits the setting request to the small cell base station when the load of the adjacent small cell base station indicated by the load information is lower than a threshold value.

  In a modification of the second embodiment, the transmitting unit is installed in the cell, and the adjacent small cell base station that is adjacent to the small cell and manages an adjacent small cell smaller than the cell is configured to transmit the small cell. An inquiry as to whether or not a user terminal establishing a connection with a base station is allowed to perform handover to the adjacent small cell base station is transmitted. The transmission unit transmits the setting request according to a response result from the adjacent small cell base station to the inquiry.

  In the modified example of the second embodiment, the transmitter, together with the inquiry, the number of user terminals predicted to be handed over to the adjacent small cell base station, and the increase in the predicted adjacent small cell base stations At least one of the load amounts is transmitted.

  In 1st Embodiment, the said transmission part transmits the said setting request | requirement with respect to the said small cell base station, when the said base station and the said small cell base station, and a user terminal can establish a pair of connection .

  In the first embodiment, as the power saving mode, a plurality of types of modes with different methods for reducing the power consumption are defined. The transmission unit transmits the setting request including mode information indicating at least one mode selected from the plurality of types of modes.

  In 1st Embodiment, the said transmission part transmits the said setting request | requirement containing the mode information which shows the mode which can communicate with a user terminal in the state where the said power consumption was reduced as the said power saving mode.

  In the first embodiment, the transmission unit transmits the setting request including time information indicating the start and / or end of the power saving mode.

  The base station (PeNB 200B) according to the first embodiment is a base station that manages cells. The base station includes a control unit that sets a power saving mode that reduces power consumption of the base station, and a large cell base station that is larger than the cell and manages a large cell in which the base station is installed inside. A receiving unit that receives the setting request for the power saving mode. The control unit sets the power saving mode based on the setting request.

  In the first embodiment, as the power saving mode, a plurality of types of modes with different methods for reducing the power consumption are defined. The reception unit receives the setting request including mode information indicating at least one mode selected from the plurality of modes. The control unit sets the power saving mode according to the mode information.

  In 1st Embodiment, the said control part performs control for the user terminal which establishes the connection with the said base station to perform the hand-over from the said base station. The control unit sets the power saving mode after the user terminal performs handover.

  In the first embodiment, as the power saving mode, a plurality of types of modes with different methods for reducing the power consumption are defined. The reception unit receives the setting request including mode information indicating at least one mode selected from the plurality of modes. The control unit determines the number of user terminals to be handed over according to the mode information.

  In the first embodiment, the receiving unit receives the setting request including time information indicating the start and / or end of the power saving mode. The control unit sets the power saving mode according to the time information.

  The base station according to the first embodiment further includes a transmission unit configured to transmit information indicating that the power saving mode is set to the large cell base station after setting the power saving mode.

[First Embodiment]
(LTE system)
FIG. 1 is a configuration diagram of an LTE system according to the present embodiment.

  1, the LTE system includes a plurality of UEs (User Equipment) 100, an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 10, and an EPC (Evolved Packet Core) 20. The E-UTRAN 10 and the EPC 20 constitute a network.

  The UE 100 is a mobile radio communication device, and performs radio communication with a cell (serving cell) that has established a connection. 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 a cell and performs radio communication with the UE 100 that has established a connection with the 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 MME (Mobility Management Entity) / S-GW (Serving-Gateway) 300 and OAM 400 (Operation and Maintenance). The EPC 20 corresponds to a core network.

  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.

  The OAM 400 is a server device managed by an operator, and performs maintenance and monitoring of the E-UTRAN 10.

  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 an antenna 101, a radio transceiver 110, a user interface 120, a GNSS (Global Navigation Satellite System) receiver 130, a battery 140, a memory 150, and a processor 160. Have. The memory 150 and the processor 160 constitute a control unit.

  The UE 100 may not have the GNSS receiver 130. Alternatively, the memory 150 may be integrated with the processor 160, and this set (ie, chip set) may be used as the processor 160 '.

  The antenna 101 and the wireless transceiver 110 are used for transmitting and receiving wireless signals. The antenna 101 includes a plurality of antenna elements. The radio transceiver 110 converts the baseband signal output from the processor 160 into a radio signal and transmits it from the antenna 101. Further, the radio transceiver 110 converts a radio signal received by the antenna 101 into a baseband signal and outputs the baseband signal 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 includes a baseband processor that modulates / demodulates and encodes / decodes a baseband signal, and a CPU (Central Processing Unit) that executes programs stored in the memory 150 and performs various processes. . The processor 160 may further include a codec that performs encoding / decoding of an audio / video signal. The processor 160 executes various processes and various communication protocols described later.

  FIG. 3 is a block diagram of the eNB 200. As illustrated in FIG. 3, the eNB 200 (including the MeNB 200 </ b> A, PeNB 200 </ b> B, and PeNB 200 </ b> B described later) includes an antenna 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 control unit. The memory 230 may be integrated with the processor 240, and this set (that is, a chip set) may be used as the processor 240 '.

  The antenna 201 and the wireless transceiver 210 are used for transmitting and receiving wireless signals. The antenna 201 includes a plurality of antenna elements. The wireless transceiver 210 converts the baseband signal output from the processor 240 into a wireless signal and transmits it from the antenna 201. In addition, the radio transceiver 210 converts a radio signal received by the antenna 201 into a baseband signal and outputs the baseband signal 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 includes a baseband processor that performs modulation / demodulation and encoding / decoding of a baseband signal, and a CPU that executes a program stored in the memory 230 and performs various processes. The processor 240 executes various processes 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. The physical layer provides a transmission service to an upper layer using a physical channel. 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 MAC scheduler that determines an uplink / downlink transport format (transport block size, modulation / coding scheme, and the like) and an allocated resource block.

  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 signals (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, otherwise, the UE 100 is in an 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 used for the downlink, and SC-FDMA (Single Carrier Frequency Multiple Access) is used for 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. A guard interval called a cyclic prefix (CP) is provided at the head of each symbol. The resource block includes a plurality of subcarriers in the frequency direction. A radio resource unit composed of one subcarrier and one symbol is called 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).

  In the downlink, the section of the first few symbols of each subframe is a control region mainly used as a physical downlink control channel (PDCCH). The remaining section of each subframe is an area that can be used mainly as a physical downlink shared channel (PDSCH). Further, cell-specific reference signals (CRS) are distributed and arranged in each subframe.

  In the uplink, both ends in the frequency direction in each subframe are control regions mainly used as a physical uplink control channel (PUCCH). Further, the central portion in the frequency direction in each subframe is an area that can be used mainly as a physical uplink shared channel (PUSCH). Further, a demodulation reference signal (DMRS) and a sounding reference signal (SRS) are arranged in each subframe.

(Operation according to the first embodiment)
(1) Operating Environment Next, the operating environment of the mobile communication system according to the present embodiment will be described with reference to FIG. FIG. 6 is an explanatory diagram for explaining an operating environment of the mobile communication system according to the first embodiment.

  As shown in FIG. 6, PeNB200B is installed in the large cell which MeNB200A manages. PeNB200B manages the small cell smaller than a large cell. PeNB200B establishes connection with UE100-1 and UE100-2. In addition, in this embodiment, UE100-1 is located in the cell edge of a small cell compared with UE100-2. An X2 interface is established between the MeNB 200A and the PeNB 200B.

  MeNB200A transmits the setting request | requirement of a power saving mode with respect to PeNB200B. PeNB200B sets a power saving mode based on the setting request | requirement of a power saving mode. The power saving mode will be described below.

(2) Power saving mode The power saving mode is a mode for reducing power consumption. In the present embodiment, as modes for reducing the power consumption of the eNB 200 (PeNB 200B), a plurality of types of modes with different methods for reducing the following power consumption are defined.

  The power saving modes include “Discontinuous Transmission (DTX)”, “Reduction of Number of Transmitting Antennas (ANT reduced)”, “Transmission Power Reduction (TxPower reduced)”, “Reduction of Communication Capacity (Capacity reduced)”, “Cell” Deactivation ”and the like.

  The intermittent transmission is a power saving mode in which the eNB 200 intermittently transmits a radio signal. FIG. 7 is a diagram for explaining intermittent transmission according to the present embodiment. As illustrated in FIG. 7, the eNB 200 intermittently transmits a cell-specific reference signal (CRS). In the example of FIG. 7, the CRS is transmitted once every 5 subframes. The eNB 200 sets a transmission stop period (DTX period) in a period (subframe) in which CRS is not transmitted. In the transmission stop period, since power supply to the radio transceiver 210 (particularly, the power amplifier) of the eNB 200 can be stopped, energy saving can be realized.

  The reduction of the number of transmission antennas is a power saving mode in which the number of antennas (hereinafter referred to as “number of used antennas”) used by the eNB 200 for transmitting radio signals is reduced. FIG. 8 is a diagram for explaining a reduction in the number of transmission antennas according to the present embodiment. As illustrated in FIG. 8, the eNB 200 transmits a radio signal using only a part of the plurality of antennas 201. By reducing the number of antennas used, the power consumption of the eNB 200 (particularly, the radio transceiver 210) is reduced, so that energy saving can be realized.

  The transmission power reduction is a power saving mode in which the eNB 200 reduces transmission power and performs redundant transmission of transmission data using surplus radio resources. By reducing the transmission power, the power consumption of the eNB 200 (particularly, the radio transceiver 210) is reduced, so that energy saving of the eNB 200 can be realized.

  The communication capacity reduction is a power saving mode in which the number of UEs that can be connected to the eNB 200 or the amount of radio resources that can be allocated by the eNB 200 is limited. By performing such a restriction, power consumption of the eNB 200 (particularly, the processor 240) is reduced, so that energy saving of the eNB 200 can be realized.

  The operation stop of the cell is a power saving mode in which the operation of the cell managed by the eNB 200 is stopped. Specifically, the eNB 200 stops transmitting radio signals. By stopping the operation of the cell, the power supply to the radio transceiver 210 (particularly, the power amplifier) of the eNB 200 can be stopped, so that energy saving can be realized. Moreover, eNB200 may stop reception from UE100 not only in transmission of a radio signal.

  The above-mentioned “intermittent transmission”, “reduction of the number of transmission antennas”, “reduction of transmission power”, and “reduction of communication capacity” are modes in which communication with the UE 100 is possible with reduced power consumption (appropriately “Partial OFF (Partial OFF)”. ) Mode).

  Note that the eNB 200 (PeNB 200B) can select at least one or more modes from a plurality of types of modes, and can set the selected mode (s) as a power saving mode.

(3) Operation Sequence Next, an operation sequence according to the present embodiment will be described with reference to FIG. FIG. 9 is a sequence diagram illustrating an example of the operation of the mobile communication system according to the first embodiment.

  As shown in FIG. 9, a pair of cells, which are combinations of cells managed by different eNBs 200 (MeNB 200A and PeNB 200B), and UE 100 are used for a dual connection (Dual Connectivity) scheme that establishes a pair of connections. A connection is established via the Xn interface. Moreover, as described above, the PeNB 200B has established a connection (RRC_CONNECTED) with the UE 100-1 and the UE 100-2. Further, the PeNB 200B does not set the power saving mode, and the switch for operating the small cell is in the on state (Switch ON).

  As shown in FIG. 9, in step S101, the MeNB 200A determines whether or not to send a power saving mode setting request to the PeNB 200B (ES determination). In this embodiment, MeNB200A determines with transmitting the setting request | requirement of a power saving mode to PeNB200B, when it can accept UE100 (s) which exist in the small cell which PeNB200B manages.

  MeNB200A determines with transmitting the setting request | requirement of a power saving mode to PeNB200B, for example in the following cases.

(A) When the load (for example, buffer capacity, traffic value, number of connected UEs, usage rate of radio resource, etc.) of the MeNB 200A is lower than the threshold (b) The number of UEs 100 connected to the PeNB 200B allows the MeNB 200A to connect When the number is less than the number of UEs 100 (c) When the UE 100 connected to the PeNB 200B can meet the QoS of the UE 100 when connected to the MeNB 200A (d) The MeNB 200A, PeNB 200B and the UE 100 establish a pair of connections When possible (when MeNB200A and PeNB200B are capable of dual connection)
(E) When the power supply status of the PeNB 200B deteriorates (for example, when the power supply of the PeNB 200B is interrupted (when the battery is driven), when the remaining battery level of the PeNB 200B falls below a specified value, or the private home of the PeNB 200B (When the output power of the generated power (solar etc.) falls below the specified value)
(F) An instruction from the host device (for example, OAM 400) of the MeNB 200

  MeNB200A may request | require information (for example, the number of UE100 connected to PeNB200B) used for the said determination to PeNB200B via a Xn interface.

  Note that the eNB 200A may determine to transmit a power saving mode setting request to the PeNB 200B in consideration of a plurality of items among the items (a) to (e).

  Below, MeNB200A assumes that it determined with transmitting the setting request | requirement of a power saving mode to PeNB200B, and advances description.

  In Step S102, the MeNB 200A transmits a power saving mode setting request (Cell Deactivation Request) for reducing power consumption to the PeNB 200B. PeNB 200B receives the setting request.

  The setting request may include mode information indicating at least one mode selected from a plurality of types of modes. Further, the setting request may include mode information (Transition) indicating a partial off mode that is a power saving mode capable of communicating with the UE 100 in a state where power consumption is reduced. For example, the mode information may be information indicating a specific power saving mode (or a combination of a plurality of specific power saving modes), or information indicating that the PeNB 200B can be arbitrarily selected. Also good. In addition, the setting request may include information (Deactivation) indicating cell operation suspension instead of the mode information.

  The setting request may include time information indicating the start and / or end of the power saving mode. The time information may be a subframe number, a system frame number, time or time, or may be a timer value indicating a set time in the power saving mode.

  Further, the setting request may include information indicating the number of UEs 100 to be handed over by the PeNB 200B (for example, an upper limit value of the number of UEs 100 that the MeNB 200 can allow a handover to, or a designated value of the number of UEs 100 to be handed over).

  In the present embodiment, the description will proceed assuming that the setting request includes mode information (Transition) indicating the partial off mode.

  In step S103, MeNB200A, PeNB200B, and UE100-1 perform a handover procedure. PeNB200B performs a handover procedure before setting a power saving mode in response to reception of mode information. Specifically, PeNB200B performs control for UE100-1 located in the cell edge side of an own cell to perform a hand-over from PeNB200B to MeNB200A. In addition, PeNB200B may set a measurement (Measurement Configuration) to UE100, in order to receive a measurement report (Measurement Report) in order to judge the position of UE100 (UE100-1 and UE100-2).

  Moreover, PeNB200B may determine the number of UE100 made to perform a hand-over according to a setting request | requirement. When the setting request does not include information indicating the number of UEs 100 to be handed over, the PeNB 200B performs handover so that the number of UEs 100 to be handed over increases according to the power consumption reduced by the power saving mode. You may determine the number of UE100 to perform. PeNB200B may determine the number of UE100 made to perform a hand-over with the number of all UE100 connected to PeNB200B, when mode information is the information which shows the operation stop of a cell.

  In step S104, connection (RRC_CONNECTED) is established between MeNB200A and UE100-1 by the completion | finish of a handover procedure.

  In step S105, the PeNB 200B sets the power saving mode based on the received setting request. Specifically, PeNB200B sets a power saving mode (partial off mode: Transition mode) according to the mode information included in the setting request. In this embodiment, PeNB200B sets a power saving mode, after UE100-1 performs a hand-over.

  PeNB200B sets a power saving mode according to time information, when a setting request | requirement contains time information. Specifically, it is set so that the power saving mode is disclosed and / or ended in accordance with the start time and / or end time of the power saving mode indicated by the time information.

  In step S106, PeNB200B transmits the response (Cell Deactivation Response) with respect to a setting request | requirement to MeNB200A. MeNB200A receives the response with respect to a setting request.

  The response to the setting request may include information indicating that the power saving mode has been set, or may include information indicating that the partial off mode has been set (Transition).

  In step S107, as in step S101, the MeNB 200A determines whether or not to send a setting request to the PeNB 200B. The MeNB 200A may determine whether to transmit a setting request to the PeNB 200B in consideration of the increased load on the MeNB 200A when the PeNB 200B performs the power saving mode. For example, the MeNB 200A may determine to transmit a setting request to the PeNB 200B when the load increase rate of the MeNB 200A before and after the PeNB 200B sets the power saving mode is lower than a threshold value.

  Hereinafter, it is assumed that the MeNB 200A determines to transmit a setting request for the power saving mode to the PeNB 200B, and the description proceeds.

  In step S108, as in step S102, the MeNB 200A transmits a setting request to the PeNB 200B. PeNB 200B receives the setting request.

  In the present embodiment, the setting request includes information (Deactivation) indicating cell operation suspension.

  In step S109, as in step S103, the MeNB 200A, PeNB 200B, and UE 100-2 execute a handover procedure. In this embodiment, since the setting request includes information indicating cell operation suspension, the PeNB 200B determines that all UEs 100 connected to the PeNB 200B are to be handed over. In the present embodiment, the PeNB 200B determines to cause the UE 100-2 to perform a handover.

  In step S110, connection (RRC_CONNECTED) is established between MeNB200A and UE100-2 by the completion | finish of a handover procedure.

  In step S111, PeNB200B sets a power saving mode similarly to step S105. In this embodiment, PeNB200B sets the power saving mode which stops operation | use of a cell. Thereby, the switch for operating the small cell is in an OFF state (Switch OFF).

  In step S112, PeNB200B transmits the response with respect to a setting request to MeNB200A similarly to step S106. MeNB200A receives the response with respect to a setting request.

  In the present embodiment, the response to the setting request includes information (Deactivation) indicating that the power saving mode for stopping the cell operation is set.

(Summary of the first embodiment)
In this embodiment, MeNB200A (radio | wireless transmitter / receiver 210) is installed in a large cell, and transmits a setting request | requirement with respect to PeNB200B which manages a small cell. Thereby, even if it becomes impossible for the UE 100 to establish a connection with the PeNB 200B by setting the power saving mode by the PeNB 200B, the UE 100 can suppress the communication from being disabled by establishing the connection with the MeNB 200A. Moreover, since PeNB200B sets a power saving mode, the power saving of PeNB200B is realizable.

  Moreover, in this embodiment, MeNB200A (radio | wireless transmitter / receiver 210) can transmit a setting request | requirement with respect to PeNB200B, when the load of MeNB200A is lower than a threshold value. Thereby, MeNB200A can fully accept UE100 from PeNB200B, Therefore UE100 does not become incommunicable and can suppress the fall of communication quality.

  Moreover, in this embodiment, MeNB200A (radio | wireless transmitter / receiver 210) can transmit a setting request | requirement with respect to PeNB200B, when MeNB200A, PeNB200B, and UE100 can establish a pair of connection. Thereby, since MeNB200A can establish a connection with UE100 connected with PeNB200B, UE100 does not become incommunicable by the establishment of the said connection, and can suppress the fall of communication quality.

  In the present embodiment, a plurality of types of modes with different methods for reducing power consumption are defined as power saving modes. MeNB200A (radio | wireless transmitter / receiver 210) can transmit the setting request | requirement containing the mode information which shows the at least 1 or more mode selected from multiple types of mode. Thereby, MeNB200A can make PeNB200B perform the power saving according to a condition.

  Moreover, in this embodiment, MeNB200A (radio | wireless transmitter / receiver 210) can transmit the setting request | requirement containing the mode information which shows the mode which can communicate with UE100 in the state by which power consumption was reduced as a power saving mode. Thereby, since PeNB200B does not stop operation of a small cell, it can suppress that UE100 connected with PeNB200B becomes incommunicable.

  Moreover, in this embodiment, MeNB200A (radio | wireless transmitter / receiver 210) can transmit the setting request | requirement containing the time information which shows the start and / or completion | finish of a power saving mode. Thereby, MeNB200A can control the time when PeNB200B performs setting mode.

  Moreover, in this embodiment, PeNB200B (radio | wireless transmitter / receiver 210) receives for the setting of the power saving mode from MeNB200A. PeNB200B (control part) sets a power saving mode based on a setting request | requirement. Thereby, even if PeNB200B sets power saving mode, MeNB200A can connect with UE100 connected to PeNB200B, Therefore The fall of the communication quality of UE100 can be suppressed.

  Moreover, in this embodiment, PeNB200B (radio | wireless transmitter / receiver 210) can receive the setting request | requirement containing the mode information which shows the at least 1 or more mode selected from multiple types of mode. PeNB200B (control part) can set a power saving mode according to mode information. Thereby, PeNB200B can aim at the power saving according to a condition.

  Moreover, in this embodiment, PeNB200B (control part) can perform control for UE100 to perform the hand-over from PeNB200B to MeNB200A. PeNB200B (control part) can set a power saving mode, after UE100 performs a hand-over. As a result, the UE 100 can perform seamless communication and can suppress a decrease in communication quality.

  Moreover, in this embodiment, PeNB200B (control part) can receive the setting request | requirement containing the mode information which shows the at least 1 or more mode selected from multiple types of mode. PeNB200B (control part) can determine the number of UE100 made to perform a handover according to mode information. Thereby, it can suppress that the load of MeNB200A increases significantly.

  Moreover, in this embodiment, PeNB200B (radio | wireless transmitter / receiver 210) can receive the setting request | requirement containing the time information which shows the start and / or completion | finish of a power saving mode. PeNB200B (control part) can set a power saving mode according to time information. Thereby, MeNB200A can control the time when PeNB200B performs setting mode.

  Moreover, in this embodiment, PeNB200B (radio | wireless transmitter / receiver 210) can transmit the information which shows having set the power saving mode to MeNB200A. Thereby, MeNB200A can confirm that PeNB200B set the power saving mode.

[Second Embodiment]
Next, the mobile communication system according to the second embodiment will be described. In addition, it demonstrates centering on a different part from embodiment mentioned above, and abbreviate | omits description for the same part suitably.

  In the embodiment described above, the MeNB 200A did not consider the eNB 200 adjacent to the PeNB 200B. However, in this embodiment, the MeNB 200A transmits a setting request to the PeNB 200B in consideration of the eNB 200 adjacent to the PeNB 200B.

(Operation according to the second embodiment)
(1) Operating environment The operating environment of the mobile communication system according to the present embodiment will be described with reference to FIG. FIG. 10 is an explanatory diagram for explaining the operating environment of the mobile communication system according to the second embodiment.

  As shown in FIG. 10, PeNB200B and PeNB200C are installed in the large cell which MeNB200A manages. Each of PeNB200B and PeNB200C manages the small cell smaller than a large cell. Moreover, PeNB200B establishes the connection with UE100. UE100 is located in the cell edge of both the small cell of PeNB200B and the small cell of PeNB200C. Moreover, the X2 interface is established between MeNB200A and PeNB200B, between MeNB200A and PeNB200C, and between PeNB200B and PeNB200C.

  MeNB200A considers PeNB200C and transmits the setting request | requirement of a power saving mode with respect to PeNB200B.

(2) Operation Sequence Next, an operation sequence according to the present embodiment will be described with reference to FIG. FIG. 11 is a sequence diagram illustrating an example of the operation of the mobile communication system according to the second embodiment.

  Similar to the first embodiment, the PeNB 200B establishes a connection (RRC_CONNECTED) with the UE 100-1 and the UE 100-2. Further, the PeNB 200B does not set the power saving mode, and the switch for operating the small cell is in the on state (Switch ON).

  As illustrated in FIG. 11, in step S201, the PeNB 200C transmits load information (for example, RESOURCE STATUS RESPONSE) indicating the load of the PeNB 200C to the MeNB 200A. PeNB200C may transmit load information via an X2 interface. In addition, PeNB200C may transmit load information according to the request (for example, RESOURCE STATUS REQUEST) from MeNB200A, may transmit load information periodically, and the load of PeNB200C is more than a threshold value. When it is low, load information may be transmitted. PeNB200C may transmit load information, when the load of PeNB200C is higher than a threshold value.

  The load information is information indicating the buffer capacity or traffic value of the PeNB 200C, for example.

  In step S202, as in step S101, the MeNB 200A determines whether or not to transmit a power saving mode setting request to the PeNB 200B.

  In this embodiment, MeNB200A determines with transmitting a setting request | requirement with respect to PeNB200B, when the load of PeNB200C is lower than a threshold value.

  Note that the MeNB 200A may determine whether or not to transmit a setting request with the reception of load information from the PeNB 200C as a trigger.

  Below, MeNB200A assumes that it determined with transmitting the setting request | requirement containing the information (Deactivation) which shows the operation stop of a cell to PeNB200B, and advances description.

  Step S203 corresponds to step S108. Note that the MeNB 200A may transmit a setting request including an instruction to transmit a handover request to the PeNB 200C.

  In step S204, as in step S103, the PeNB 200B, the PeNB 200C, and the UE 100 execute a handover procedure.

  In step S205, connection (RRC_CONNECTED) is established between PeNB200C and UE100 by the completion | finish of a handover procedure.

  Steps S206 and S207 correspond to steps S111 and S112.

(Operation according to a modified example of the second embodiment)
Next, an operation according to a modified example of the second embodiment will be described with reference to FIG. FIG. 12 is a sequence diagram illustrating an example of the operation of the mobile communication system according to the modified example of the second embodiment.

  The description will focus on parts that are different from the first and second embodiments described above, and description of similar parts will be omitted as appropriate.

  In the second embodiment described above, the MeNB 200A determines whether to transmit a setting request to the PeNB 200B based on the load information of the PeNB 200C adjacent to the PeNB 200B. In this embodiment, MeNB200A transmits an inquiry with respect to PeNB200B in order to determine whether a setting request | requirement is transmitted.

  In step S301, the MeNB 200A transmits an inquiry (Inquiry message) to the PeNB 200C as to whether or not the UE 100 establishing the connection with the PeNB 200B is allowed to perform a handover to the PeNB 200C.

  The MeNB 200A may transmit to the PeNB 200C at least one of the number of UEs 100 predicted to be handed over to the PeNB 200C and the predicted increased load amount of the PeNB 200C together with the inquiry.

  MeNB200A may determine the number of UE100 estimated to be handed over to PeNB200C according to the positional information on UE100. Moreover, MeNB200A may determine the increase load amount of PeNB200C estimated based on the load of PeNB200B.

  In addition, MeNB200A may determine adjacent eNB200 which makes an inquiry based on the measurement report (Measurement Report) of UE100 which establishes the connection with PeNB200B received from PeNB200B, for example.

  In step S302, the PeNB 200C determines whether or not the UE 100 that establishes a connection with the PeNB 200B is allowed to perform a handover to the PeNB 200C. The PeNB 200C may determine that the handover is permitted when the load of the PeNB 200C is lower than the threshold. Further, the PeNB 200B may determine whether or not to allow handover based on at least one of the predicted number of UEs 100 and the predicted increased load amount.

  In the present embodiment, the PeNB 200C will be described assuming that it is determined that the handover is permitted.

  In step S303, the PeNB 200C transmits a response to the inquiry (Inquiry message Response) to the MeNB 200A. MeNB200A receives the response with respect to an inquiry.

  In the present embodiment, the response to the inquiry includes information indicating that the handover is permitted.

  In step S304, the MeNB 200A determines whether or not to transmit a setting request in response to a response to the inquiry that is a response result from the PeNB 200C to the inquiry.

  Specifically, the MeNB 200A determines that a setting request is to be transmitted when the PeNB 200C allows handover, and determines that the setting request is not transmitted when the PeNB 200C does not allow handover.

  Steps S305 to S309 correspond to steps S203 to S207 of the second embodiment.

(Summary of the second embodiment)
In this embodiment, MeNB200A (radio | wireless transmitter / receiver 210) can receive the load information which shows the load of PeNB200C. MeNB200A (radio | wireless transmitter / receiver 210) can transmit a setting request | requirement with respect to PeNB200B, when the load of PeNB200C is lower than a threshold value. Thereby, MeNB200A can determine whether the setting request | requirement is transmitted considering UE100 which hands over from PeNB200B to PeNB200C.

  Moreover, in the modification of this embodiment, MeNB200A (radio | wireless transmitter / receiver 210) can transmit the inquiry of whether UE100 which establishes a connection with PeNB200B accept | permits handing over to PeNB200C with respect to PeNB200C. It is. MeNB200A (radio | wireless transmitter / receiver 210) can transmit a setting request | requirement according to the reply result from PeNB200C with respect to an inquiry. Thereby, MeNB200A can determine whether the setting request | requirement is transmitted in consideration of the state of PeNB200B.

  Moreover, in the modification of this embodiment, MeNB200A (radio | wireless transmitter / receiver 210) transmits at least one of the number of UE100 estimated to be handed over to PeNB200C and the increase load amount of predicted PeNB200C with an inquiry. Is possible. Thereby, PeNB200C can determine appropriately whether it accept | permits performing a handover according to the condition of PeNB200B.

[Other embodiments]
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the MeNB 200A determines whether or not to transmit a setting request, but a network device (an upper device (eg, MME) or a determination server of the MeNB 200A) performs the determination. Also good.

  Further, the first embodiment and the second embodiment described above may be implemented in appropriate combination. For example, the MeNB 200A may determine whether to transmit a setting request based on the load of the MeNB 200A and the load of the PeNB 200C.

  In the above-described embodiment, an example in which the present invention is applied to the LTE system has been 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.

  DESCRIPTION OF SYMBOLS 10 ... E-UTRAN, 20 ... EPC, 100, 100-1, 100-2, 100-3 ... UE (user terminal), 101 ... Antenna, 110 ... Radio transceiver, 120 ... User interface, 130 ... GNSS receiver 140 ... battery 150 ... memory 160,160 '... processor 200,200-1,200-2,200-3 ... eNB (radio base station), 200A ... MeNB, 200B, 200C ... PeNB, 201 ... antenna 210 ... Wireless transceiver 220 ... Network interface 230 ... Memory 240, 240 '... Processor 300 ... MME / S-GW 400 ... OAM

Claims (15)

A base station managing a cell,
A transmission unit that transmits a setting request for a power saving mode for reducing power consumption,
The base station, wherein the transmission unit is installed in the cell and transmits the setting request to a small cell base station that manages a small cell smaller than the cell.   The base station according to claim 1, wherein the transmission unit transmits the setting request to the small cell base station when a load on the base station is lower than a threshold value. A receiver configured to receive load information indicating a load of the adjacent small cell base station from an adjacent small cell base station that is installed in the cell and that manages an adjacent small cell that is adjacent to the small cell and is smaller than the cell; ,
The transmission unit transmits the setting request to the small cell base station when a load of the adjacent small cell base station indicated by the load information is lower than a threshold value. The listed base station. The transmitter is installed in the cell, and establishes connection with the small cell base station for an adjacent small cell base station that is adjacent to the small cell and manages an adjacent small cell smaller than the cell. Send an inquiry as to whether or not to allow the terminal to perform handover to the adjacent small cell base station,
The base station according to claim 1, wherein the transmission unit transmits the setting request according to a response result from the adjacent small cell base station to the inquiry.   The transmitting unit transmits at least one of the number of user terminals predicted to be handed over to the adjacent small cell base station and the predicted increased load amount of the adjacent small cell base station together with the inquiry. The base station according to claim 4.   The transmission unit transmits the setting request to the small cell base station when the base station and the small cell base station and a user terminal can establish a pair of connections. Item 4. The base station according to Item 1. As the power saving mode, a plurality of types of modes with different methods for reducing the power consumption are defined,
The base station according to claim 1, wherein the transmission unit transmits the setting request including mode information indicating at least one mode selected from the plurality of modes.   The said transmission part transmits the said setting request | requirement containing the mode information which shows the mode which can communicate with a user terminal in the state in which the said power consumption was reduced as the said power saving mode. base station.   The base station according to claim 1, wherein the transmission unit transmits the setting request including time information indicating start and / or end of the power saving mode. A base station managing a cell,
A control unit for setting a power saving mode for reducing power consumption of the base station;
A receiving unit that receives a setting request for the power saving mode from a large cell base station that is larger than the cell and that manages a large cell in which the base station is installed inside;
The base station, wherein the control unit sets the power saving mode based on the setting request. As the power saving mode, a plurality of types of modes with different methods for reducing the power consumption are defined,
The receiving unit receives the setting request including mode information indicating at least one mode selected from the plurality of modes.
The base station according to claim 10, wherein the control unit sets the power saving mode according to the mode information. The control unit performs control for a user terminal establishing a connection with the base station to perform a handover from the base station,
The base station according to claim 10, wherein the control unit sets the power saving mode after the user terminal performs handover. As the power saving mode, a plurality of types of modes with different methods for reducing the power consumption are defined,
The receiving unit receives the setting request including mode information indicating at least one mode selected from the plurality of modes.
The base station according to claim 12, wherein the control unit determines the number of user terminals to be handed over according to the mode information. The receiving unit receives the setting request including time information indicating start and / or end of the power saving mode;
The base station according to claim 10, wherein the control unit sets the power saving mode according to the time information.   The base station according to claim 10, further comprising: a transmission unit configured to transmit information indicating that the power saving mode is set to the large cell base station after setting the power saving mode.

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