JP2015159380A - Mobile communication system and network device - Google Patents

Abstract

A mobile communication system and a network device that can efficiently use radio resources while reducing deterioration of signal quality due to delay dispersion.
In a mobile communication system, an MBSFN area is configured by a plurality of cells that transmit MBSFN (MBMS Single Frequency Network) reference signals. A network device configured to set an MBSFN reference signal resource amount that is an amount of time / frequency resources of the MBSFN reference signal in the frequency direction; The network device sets the MBSFN reference signal resource amount based on coverage information regarding each coverage size of the plurality of cells.
[Selection] Figure 8

Description

  The present invention relates to a mobile communication system having a plurality of base stations constituting an MBSFN, and a network device.

  In 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, standardization of eMBMS (evolved MBMS), which is an advanced version of MBMS (Multimedia Broadcast Multicast Service), is in progress (for example, non-patent document 1).

  In such a mobile communication system, a plurality of base stations (cells) constituting an MBSFN (MBMS Single Frequency Network) distribute multimedia data by simultaneously transmitting the same signal. With such an MBSFN transmission method, a user terminal can perform RF (Radio Frequency) synthesis on signals transmitted from a plurality of base stations.

3GPP Technical Specification “TS 36.300 v12.0.0” (2014-1)

  In MBSFN, since the same signal is transmitted from a plurality of base stations, signal quality is greatly degraded based on delay dispersion. For this reason, each of the plurality of base stations transmits the MBSFN reference signal using more radio resources than the transmission of the normal reference signal.

  However, since many radio resources are used for transmitting the MBSFN reference signal, there is a problem that, for example, radio resources used for multimedia data distribution are reduced.

  Therefore, the present invention provides a mobile communication system and a network device that can efficiently use radio resources while reducing deterioration of signal quality based on delay dispersion.

  In the mobile communication system according to an embodiment, an MBSFN area is configured by a plurality of cells that transmit MBSFN (MBMS Single Frequency Network) reference signals. The mobile communication system includes a network device that sets an MBSFN reference signal resource amount that is an amount of time / frequency resources of the MBSFN reference signal in the frequency direction. The network device sets the MBSFN reference signal resource amount based on coverage information regarding each coverage size of the plurality of cells.

  According to the mobile communication system and the network device according to the present invention, it is possible to reduce radio resources used for transmitting an MBSFN reference signal while reducing deterioration of signal quality based on delay dispersion.

FIG. 1 is a configuration diagram of an LTE system according to the embodiment. FIG. 2 is a block diagram of the UE according to the embodiment. FIG. 3 is a block diagram of the eNB according to the embodiment. 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 the architecture of eMBMS according to the embodiment. FIG. 7 is a diagram illustrating an operating environment according to the embodiment. FIG. 8 is a sequence diagram for explaining an operation pattern 1 according to the embodiment. FIG. 9 is a flowchart for determining the MBSFN reference signal resource amount according to the embodiment. FIG. 10 is an explanatory diagram for explaining an example of the radio resource of the MBSFN reference signal. FIG. 11 is a sequence diagram for explaining an operation pattern 2 according to the embodiment. FIG. 12 is a sequence diagram for explaining an operation pattern 3 according to the embodiment.

[Outline of Embodiment]
In the mobile communication system according to the embodiment, an MBSFN area is configured by a plurality of cells that transmit MBSFN (MBMS Single Frequency Network) reference signals. The mobile communication system includes a network device that sets an MBSFN reference signal resource amount that is an amount of time / frequency resources of the MBSFN reference signal in the frequency direction. The network device sets the MBSFN reference signal resource amount based on coverage information regarding each coverage size of the plurality of cells.

  In the embodiment, the network device reduces the MBSFN reference signal resource amount when the coverage size indicated by the coverage information is less than a threshold value, compared to when the coverage size indicated by the coverage information is equal to or greater than the threshold value. Set.

  In the embodiment, when the maximum coverage size among the coverage sizes of each of the plurality of cells is less than the threshold, the network device is more than the case where the maximum coverage size is equal to or greater than the threshold. The MBSFN reference signal resource amount is set to be small.

  In the embodiment, the coverage information includes frequency information indicating a height of a frequency to which each of the plurality of cells belongs, and the network device has a frequency height indicated by the frequency information equal to or higher than a threshold value. The MBSFN reference signal resource amount is set to be smaller than when the frequency height indicated by the frequency information is less than the threshold.

  The mobile communication system according to the embodiment further includes a base station that manages a predetermined cell included in the plurality of cells. The base station transmits information indicating the transmission power of the predetermined cell to the network device as the coverage information.

  The mobile communication system according to the embodiment further includes a base station that manages a predetermined cell included in the plurality of cells. The base station transmits the coverage information to the network device triggered by the start of operation of the predetermined cell.

  In the embodiment, the base station transmits the coverage information to the network device in response to a request from the network device.

  The mobile communication system according to the embodiment further includes a user terminal located in any one of the plurality of cells, and a base station that manages the cell where the user terminal is located. The base station receives the coverage information from the user terminal and transmits the received coverage information to the network device.

  In the embodiment, the base station transmits a transmission request for the coverage information to the user terminal in response to reception of the first request from the network device. The user terminal transmits the coverage information to the base station in response to reception of the coverage information transmission request.

  In the embodiment, the base station transmits the coverage information received from the user terminal to the network device in response to receiving a second request from the network device.

  In the embodiment, the user terminal acquires timing information for adjusting the transmission timing of the user terminal, and the user terminal uses the timing information acquired when connecting to the base station as the coverage information. Information is transmitted to the base station.

  The mobile communication system according to the embodiment further includes a base station that manages any one of the plurality of cells. When changing the MBSFN reference signal resource amount, the network device notifies the base station of information related to the change of the MBSFN reference signal resource amount.

  In an embodiment, the network device is a macro base station that manages macro cells that overlap each of the plurality.

  The mobile communication system according to the embodiment further includes a user terminal located in the cell managed by the base station. The macro base station broadcasts to the user terminal information related to the change of the MBSFN reference signal resource amount.

  The network device according to the embodiment is used in a mobile communication system in which an MBSFN area is configured by a plurality of cells that transmit MBSFN (MBMS Single Frequency Network) reference signals. The network apparatus includes a control unit that sets an MBSFN reference signal resource amount that is an amount of time / frequency resources of the MBSFN reference signal in the frequency direction. The control unit sets the MBSFN reference signal resource amount based on coverage information regarding each coverage size of the plurality of cells.

[Embodiment]
Hereinafter, an embodiment in which the present invention is applied to an LTE (Long Term Evolution) system, which is one of mobile communication systems configured in accordance with the 3GPP standard, will be described with reference to the drawings.

(LTE system)
FIG. 1 is a configuration diagram of an LTE system according to the first 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 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. EPC20 comprised by MME / S-GW300 accommodates eNB200.

  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 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. 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 antenna 101 and the wireless transceiver 110 are used for transmitting and receiving wireless signals. 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 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 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. 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. 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) for transmitting a control signal. The remaining section of each subframe is an area that can be used as a physical downlink shared channel (PDSCH) mainly for transmitting user data.

  In the uplink, both ends in the frequency direction in each subframe are control regions mainly used as a physical uplink control channel (PUCCH) for transmitting a control signal. Further, the central portion in the frequency direction in each subframe is an area that can be used as a physical uplink shared channel (PUSCH) mainly for transmitting user data.

(MBMS)
MBMS is a bearer service that realizes multicast distribution. The network can improve the network efficiency and the frequency utilization efficiency by simultaneously delivering the MBMS service to a plurality of UEs that desire to receive the MBMS service using a common bearer. In addition, a plurality of eNBs 200 (cells) constituting an MBSFN (MBMS Single Frequency Network) area transmit the same signal all at once, so that the UE 100 can perform RF synthesis on the signals transmitted from the respective eNBs 200.

  As logical channels for MBMS, MTCH (Multicast Traffic Channel) and MCCH (Multicast Control Channel) are defined. In addition, as a transport channel for MBMS, MCH (Multicast Channel) is defined. The eNB 200 distributes the MBMS service and MBMS control information for controlling the MBMS service distribution via the multicast channels (MTCH and MCCH).

  FIG. 6 is an explanatory diagram for explaining the architecture of eMBMS according to the present embodiment. As shown in FIG. 6, the architecture of the eMBMS according to the present embodiment is a centralized architecture (Centralized MCE architecture). Specifically, each eNB 200 is connected to an MCE (Multi-Cell / Multicast Coordination Entity). The MCE is a logical entity and is provided in a stand-alone physical entity or another physical entity. In this embodiment, MCE is provided in MeNB200 which manages a macrocell.

  The MCE controls the MBSFN area. Specifically, the MCE approves / rejects participation of the eNB 200 in the MBSFN area, or assigns radio resources used in each eNB 200 in the MBMSF area. Further, the MCE sets the amount of time / frequency resources (hereinafter referred to as MBSFN reference signal resources) of the MBSFN reference signal, as will be described later.

(Operation according to the embodiment)
Hereinafter, an operation according to the present embodiment will be described. Specifically, operation patterns 1 to 3 according to the present embodiment will be described. Note that the following operation patterns will be described with a focus on differences from the other operation patterns, and description of similar portions will be omitted as appropriate.

  FIG. 7 is a diagram showing an operating environment according to the present embodiment. As illustrated in FIG. 7, the MeNB 200 manages a macro cell, and each of the plurality of eNBs 200 (eNBs 200-1 to 200-3) manages a cell (Small Cell). Each of the plurality of eNBs 200 is installed in a macro cell. Further, the macro cell overlaps with each of the plurality of cells.

  Each of the plurality of cells (eNB 200) transmits an MBSFN reference signal. An MBSFN area is constituted by a plurality of cells. MeNB200 is provided with MCE and controls the MBSFN area comprised by a some cell. The UE 100 is located in any one of a plurality of cells.

(1) Operation pattern 1
The operation pattern 1 will be described with reference to FIGS. FIG. 8 is a sequence diagram for explaining an operation pattern 1 according to the present embodiment. FIG. 9 is a flowchart for determining the MBSFN reference signal resource amount according to the present embodiment. FIG. 10 is an explanatory diagram for explaining an example of the radio resource of the MBSFN reference signal.

  The operation pattern 1 is an operation pattern in a case where the newly installed eNB 200-2 configures an MBSFN area with another eNB 200-1 (and the eNB 200-3). Note that the operation of the eNB 200-3 is the same as that of the eNB 200-1, and a description thereof will be omitted.

  The description will proceed assuming that the UE 100-1 is in the cell managed by the eNB 200-1 and the UE 100-2 is in the cell managed by the eNB 200-2.

  As illustrated in FIG. 8, in step S101, the newly installed eNB 200-2 transmits coverage information regarding the coverage size to the MeNB 200, triggered by the start of cell operation. eNB200-2 may transmit coverage information to MeNB200 at the timing which communicates with MeNB200, before starting operation | movement of a cell after being installed.

  In the present embodiment, the coverage information includes, for example, radius information indicating a cell radius and an identifier (Cell ID) of the cell. The radius information is, for example, transmission power information indicating cell transmission power.

  The coverage information may include frequency information indicating the height of the frequency to which the cell belongs as option information. The frequency information is, for example, information indicating a cell frequency band (800 MHz band, 2 GHz band, etc.).

  In step S102, the MeNB 200 sets the MBSFN reference signal resource amount based on the coverage information. Specifically, the MBSFN reference signal resource amount is set as follows.

  As illustrated in FIG. 9, in step S201, the MeNB 200 calculates the coverage size of the cell of the eNB 200-2 based on the coverage information (radius information Rx) from the eNB 200-2.

  Next, MeNB200 calculates the largest coverage size among the coverage sizes of the some cell which comprises an MBSFN area.

  In step S202, the MeNB 200 compares the maximum coverage size (max (Rx)) with a threshold value. MeNB200 performs the process of step S203, when the largest coverage size is less than a threshold value, and when that is not right, it waits for reception of coverage information.

  Here, the threshold value is a value determined according to delay dispersion. For example, the threshold value is determined such that signal quality degradation based on delay dispersion is less than a predetermined value.

  In step S203, the MeNB 200 changes (sets) the MBSFN reference signal resource amount in the frequency direction.

  Specifically, the MeNB 200 sets the amount of MBSFN reference signal resources in the frequency direction shown in FIG. 10A as a standard resource amount. This standard resource amount is a larger value than the radio resource amount used for a normal cell reference signal (CRS). MeNB200 sets this standard resource amount, when the maximum coverage size is more than a threshold value. For example, the MeNB 200 sets the MBSFN reference signal resource amount so that the resource block (RB) interval in the frequency direction is 15 kHz.

  In step S203, since the maximum coverage size is less than the threshold, the MeNB 200 changes (sets) the MBSFN reference signal resource amount to an amount smaller than the standard resource amount as illustrated in FIG. In addition, the resource block shown with the oblique line in FIG.10 (b) is a radio | wireless resource reduced from the MBSFN reference signal resource of Fig.10 (a).

  When the coverage information includes frequency information, the MBSFN reference signal resource amount may be adjusted according to the frequency information. Specifically, since the delay dispersion increases as the frequency band to which the cell belongs is lower, when the frequency height indicated by the frequency information is less than the threshold (that is, when the cell is in a lower frequency band), refer to MBSFN. A large amount of signal resources may be set (adjusted). On the other hand, when the frequency height indicated by the frequency information is equal to or higher than the threshold (that is, when the cell is in a high frequency band), the MBSFN reference signal resource amount may be set (adjusted) to be small.

  Returning to the description of FIG. As described above, the MeNB 200 sets the MBSFN reference signal resource amount, whereby the arrangement pattern of the MBSFN reference signal resources is determined. One arrangement pattern may be determined according to the MBSFN reference signal resource amount, or the MeNB 200 may determine one arrangement pattern from among a plurality of arrangement patterns corresponding to the MBSFN reference signal resource amount. The determined arrangement pattern is applied in common to cells constituting the same MBSFN area.

  In step S103, the MeNB 200 stores (registers) the coverage information received from the eNB 200-2. Coverage information is stored for each cell.

  In step S104, when changing the MBSFN reference signal resource amount, the MeNB 200 notifies each eNB 200 of change information regarding the change of the MBSFN reference signal resource amount. MeNB200 notifies change information, for example using X2 interface (X2 message format).

  The change information is information indicating the MBSFN reference signal resource arrangement pattern after the change. Specifically, the change information may be information on the arrangement pattern itself or a parameter indicating the arrangement pattern. Alternatively, it may be information indicating that the MBSFN reference signal resource amount (MBSFN reference signal resource arrangement pattern) has been changed. In this case, the eNB 200 storing the arrangement pattern of the two MBSFN reference signal resources changes to an arrangement pattern different from the applied arrangement pattern.

  Further, the change information may include information indicating the timing at which the eNB 200 applies the arrangement pattern. Thereby, the plurality of eNBs 200 can change the arrangement pattern at the same timing.

  Each eNB 200 that has received the change information from the MeNB 200 changes (applies) the arrangement pattern of the MBSFN reference signal resources based on the change information.

  In step S105, each eNB 200 transmits the change information described above to the UE 100 by broadcast or unicast. For example, the eNB 200 transmits the change information by broadcast using the message format of the SIB13.

  Based on the change information received from the eNB 200, the UE 100 performs settings for receiving the MBSFN reference signal resource.

  Thereafter, each eNB 200 transmits an MBSFN reference signal in accordance with the changed MBSFN reference signal resource arrangement pattern. The UE 100 receives the MBSFN reference signal based on the changed setting.

  Each eNB 200 can use the remaining radio resources to transmit user data and / or control data for MBMS by setting the MBSFN reference signal resource amount small.

(2) Operation pattern 2
Next, the operation pattern 2 will be described with reference to FIG. FIG. 11 is a sequence diagram for explaining an operation pattern 2 according to the present embodiment.

  In the operation pattern 1, the eNB 200-2 has transmitted to the MeNB 200 using the start of cell operation as a trigger. In the operation pattern 2, the eNB 200 transmits coverage information in response to a request from the MeNB 200.

  As illustrated in FIG. 11, in step S301, the MeNB 200 requests a coverage information (radius information request) from each eNB 200 configuring the MBSFN area. MeNB200 can perform a radius information request | requirement, when eNB200 is installed or it knows that eNB200 started operation | use of a cell. MeNB200 may perform a radius information request | requirement with a predetermined period.

  In step S302, the eNB 200 transmits coverage information to the MeNB 200 in response to the radius information request.

  Steps S303 to S306 correspond to steps S102 to S105.

(3) Operation pattern 3
Next, the operation pattern 3 will be described with reference to FIG. FIG. 12 is a sequence diagram for explaining an operation pattern 3 according to the present embodiment.

  In the operation pattern 1, the transmission source that transmits the coverage information is the eNB 200. In the operation pattern 3, the transmission source that transmits the coverage information is the UE 100.

  As shown in FIG. 12, in step S401, the MeNB 200 transmits a request transmission request to each eNB 200 configuring the MBSFN area. The request transmission request is a request for transmission of coverage information from the UE 100. The MeNB 200 can make a request transmission request at the same timing as the radius information request.

  In step S402, each eNB 200 makes a request for coverage information (radius information request) to the UE 100 located in its own cell in response to receiving the request transmission request.

  In step S403, each UE 100 notifies (transmits) the coverage information to the eNB 200 in response to the reception of the radius information request.

  In this embodiment, coverage information is timing information for adjusting the transmission timing of the UE 100. UE100 acquires timing information, when connecting to eNB200. Specifically, UE100-1 acquires the timing advance (TA) which is timing information from eNB200-1 by performing the random access procedure (RACH process) for establishing a connection with eNB200-1.

  eNB200-1 receives the coverage information from UE100-1, and eNB200-2 receives the coverage information from UE100-2. Each eNB 200 holds the received coverage information.

  In step S404, the MeNB 200 makes a request for coverage information (radius information request) to each eNB 200, similarly to step S301. In the present embodiment, each eNB 200 holds the coverage information from the UE 100 without transmitting it to the MeNB 200 until a radius information request is received from the MeNB 200.

  Steps S405 to S409 correspond to steps S302 to S306. In S406, the MeNB 200 can set the MBSFN reference signal resource amount depending on whether or not the maximum timing advance is equal to or greater than the threshold, as in S102 of the operation pattern 1 described above.

(Summary of embodiment)
The greater the amount of radio resources in the frequency direction, the more the signal quality degradation based on delay dispersion can be reduced. On the other hand, the delay dispersion increases in proportion to the communication distance (communication radius), and therefore, when the coverage size is small, that is, when the communication distance of the cell is small, the delay dispersion is small, so the signal quality is degraded based on the delay dispersion. do not do.

  In this embodiment, MeNB200 (MCE) sets the MBSFN reference signal resource amount in a frequency direction based on the coverage information regarding each coverage size of a some cell. Thereby, since MeNB200 can set the MBSFN reference signal resource amount appropriately based on the communication distance of a cell, it can reduce signal quality degradation based on delay dispersion. Moreover, since the radio resource that has not been used as the radio resource for the MBSFN reference signal can be used, for example, to transmit user data and / or control data for MBMS, the radio resource can be efficiently used. it can.

  In the present embodiment, the MeNB 200 can set the MBSFN reference signal resource amount smaller when the coverage size indicated by the coverage information is less than the threshold, compared to when the coverage size is greater than or equal to the threshold. As a result, when the coverage size is less than the threshold value, the signal quality does not deteriorate based on the delay dispersion, and therefore, the MBSFN reference signal resource amount can be set smaller than when the signal quality deteriorates based on the delay dispersion. it can. As a result, radio resources can be used efficiently.

  In this embodiment, the MeNB 200 determines that the maximum coverage size is less than the threshold when the maximum coverage size is less than the threshold among the coverage sizes of each of the plurality of cells. The MBSFN reference signal resource amount can be set smaller than in the case where it is equal to or greater than the threshold value. As a result, if the maximum coverage size is less than the threshold, the MeNB 200 can simplify the process for setting the MBSFN reference signal resource amount because the other coverage sizes are also less than the threshold.

  In the present embodiment, the coverage information includes frequency information. MeNB200 can set MBSFN reference signal resource amount small, when the frequency height which frequency information shows is more than a threshold value compared with the case where the frequency height which frequency information shows is less than a threshold value. As a result, the delay dispersion becomes larger as the frequency is lower. Therefore, the MBSFN reference signal resource amount can be appropriately set based on the height of the frequency. It can be used efficiently.

  In the present embodiment, the eNB 200 transmits coverage information to the MeNB 200 using a start of cell operation as a trigger. Accordingly, the MeNB 200 can appropriately set the MBSFN reference signal resource amount even when a new cell joins the MBSFN area.

  In this embodiment, eNB200 transmits a radius information request | requirement to UE100 according to reception of the 1st request | requirement (request transmission request) from MeNB200. The UE 100 transmits coverage information to the eNB 200 in response to receiving the radius information request. Thereby, MeNB200 can reduce the unnecessary signaling from eNB200 by making the said request | requirement, when coverage information is required.

  In this embodiment, eNB200 transmits coverage information to MeNB200 according to the 2nd request | requirement (radius information request | requirement) from MeNB200. Thereby, MeNB200 can reduce the unnecessary signaling from eNB200 by making the said request | requirement, when coverage information is required.

  In this embodiment, eNB200 transmits the information which shows the transmission power of an own cell to MeNB200 as coverage information. Thereby, since the communication distance of a cell can be estimated from the transmission power of the cell, the MeNB 200 can appropriately set the MBSFN reference signal resource amount based on the transmission power of the cell.

  In this embodiment, eNB200 receives coverage information from UE100, and transmits the received coverage information to MeNB200. Thereby, since the communication distance of a cell can be estimated from UE100 based on coverage information, MeNB200 can set a MBSFN reference signal resource amount appropriately based on an actual communication environment.

  In this embodiment, eNB200 transmits the coverage information from UE100 to MeNB200 according to the request | requirement from MeNB200. Thereby, MeNB200 can reduce the unnecessary signaling from eNB200 by making the said request | requirement, when coverage information is required.

  In this embodiment, UE100 transmits the timing information acquired when connecting with eNB200 to eNB200 as coverage information. Accordingly, since the communication distance of the cell can be estimated based on the timing advance, the MeNB 200 can appropriately set the MBSFN reference signal resource amount based on the actual communication environment.

  In this embodiment, MeNB200 notifies change information with respect to each eNB200, when changing MBSFN reference signal resource amount. Accordingly, each eNB 200 configuring the MBSFN area can know the arrangement pattern of the MBSFN reference signal resources based on the change information, and therefore can transmit the MBSFN reference signal with an appropriate amount of MBSFN reference signal resources. .

[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.

  In the embodiment described above, the MeNB 200 sets the MBSFN reference signal resource amount by comparing the maximum coverage size with a threshold, but is not limited thereto. The MBSFN reference signal resource amount may be set by comparing the coverage size of each cell with a threshold without calculating the maximum coverage. MeNB200 sets the amount of MBSFN reference signal resources to a standard resource amount when at least one of the plurality of cells constituting the MBSFN area exceeds a threshold. Accordingly, the MeNB 200 sets the amount of the MBSFN reference signal resource to be smaller than the standard resource amount when all the cells out of the plurality of cells constituting the MBSFN area exceed the threshold.

  Alternatively, the MeNB 200 compares the coverage size indicated by the newly received coverage information with the threshold without re-comparing the coverage size indicated by the known coverage information with the threshold, and determines the set MBSFN reference signal resource amount. You may determine whether to change.

  In addition, the MeNB 200 has changed the MBSFN reference signal resource amount in the frequency direction, but may change the MBSFN reference signal resource amount in the time direction.

  Further, the MeNB 200 may set the MBSFN reference signal resource amount in the frequency direction according to the maximum coverage size. Specifically, the MBSFN reference signal resource amount in the frequency direction may be set to increase as the maximum coverage size increases.

  In the embodiment described above, the eNB 200 transmits the change information to the UE 100, but is not limited thereto. MeNB200 provided with MCE may notify change information to UE100 by broadcast, when managing the macrocell which overlaps with each of the some cell which comprises an MBSFN area. Thereby, since the process which transmits change information from eNB200 to UE100 can be abbreviate | omitted, the amount of MBSFN reference signal resources can be changed rapidly.

  Note that the MeNB 200 can transmit the change information by broadcast using, for example, the message format of the SIB13.

  In the above-described embodiment, the MCE is provided in the MeNB 200, but is not limited thereto. The MCE may be provided in a stand-alone network device (for example, a management server) that is not an eNB. In this case, the MCE notifies the eNB 200 of the change information using the M2 interface (M2 message format).

  Moreover, in the operation pattern 1 of the embodiment described above, the eNB 200-2 may transmit coverage information to the MeNB 200 (MCE) when the own cell participates in the MBSFN area.

  Further, in the operation pattern 3 of the above-described embodiment, the timing information is information received from the UE 100, but is not limited thereto. The eNB 200 may retain the timing advance transmitted to the UE 100 during the random access procedure, and may transmit the retained timing advance to the MeNB 200 as coverage information in response to a request from the MeNB 200, for example.

  In the above-described embodiment, the coverage information may be calculated based on, for example, a path loss between the eNB 200 and the UE 100. A path loss (coverage information) may be calculated based on the difference between the transmission power from the UE 100 and the reception power of the eNB 200.

  Or UE100 may transmit to eNB200 as position information at the time of handing over to eNB200. The eNB 200 may calculate coverage information based on the distance between the position of the eNB 200 and the position when the UE 100 is handed over to the eNB 200.

  Further, the coverage information may be a type of each of a plurality of cells (macro cell, small cell, pico cell, etc.). For example, when a plurality of cells includes a macro cell, the MCE can set the standard resource amount as the amount of MBSFN reference signal resources.

  The coverage information may be the reception status (reception quality) of the MBMS service from the UE 100 that uses the MBMS service. When the reception quality of the MBMS service is poor, the UE 100 notifies the eNB 200 of coverage information including quality information indicating that the reception quality of the MBMS service is poor and location information of the UE 100 when the reception quality of the MBMS service is poor. . The MCE can set a large amount of MBSFN reference signal resources based on the coverage information.

  Note that the UE 100 may transmit coverage information further including an MBMSFN area index acquired by SIB from the eNB 200 configuring the MBMSFN area, in addition to the quality information and the location information.

  Further, the coverage information may include, as option information, antenna information related to an antenna that forms at least one of a plurality of cells constituting the MBMSFN area. The antenna information includes information indicating the height of the antenna, information indicating the angle (tilt angle) of the antenna, and the like. For example, the threshold to be compared with the coverage size may be adjusted so that the threshold decreases according to the height of the antenna.

  In the above-described embodiment, the MCE may set the MBSFN reference signal resource amount based on the above-described multiple types of coverage information.

  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.

  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) 201 ... antenna 210 ... radio transceiver 220 ... network Interface 230 ... Memory 240, 240 '... Processor 300 ... MME / S-GW

Claims (15)

A mobile communication system in which an MBSFN area is configured by a plurality of cells that transmit MBSFN (MBMS Single Frequency Network) reference signals,
A network device for setting an MBSFN reference signal resource amount which is an amount of time / frequency resources of the MBSFN reference signal in the frequency direction;
The mobile communication system, wherein the network device sets the MBSFN reference signal resource amount based on coverage information regarding a coverage size of each of the plurality of cells.   When the coverage size indicated by the coverage information is less than a threshold, the network device sets the MBSFN reference signal resource amount to be smaller than when the coverage size indicated by the coverage information is equal to or greater than the threshold. The mobile communication system according to claim 1, characterized in that:   When the maximum coverage size among the coverage sizes of each of the plurality of cells is less than the threshold, the network device can compare the MBSFN reference signal compared with the case where the maximum coverage size is equal to or greater than the threshold. The mobile communication system according to claim 2, wherein the resource amount is set to be small. The coverage information includes frequency information indicating a height of a frequency to which each of the plurality of cells belongs,
The network device reduces the MBSFN reference signal resource amount when the frequency height indicated by the frequency information is greater than or equal to a threshold value compared to when the frequency height indicated by the frequency information is less than the threshold value. The mobile communication system according to claim 1, wherein the mobile communication system is set. A base station for managing a predetermined cell included in the plurality of cells;
The mobile communication system according to claim 1, wherein the base station transmits information indicating transmission power of the predetermined cell to the network device as the coverage information. A base station for managing a predetermined cell included in the plurality of cells;
2. The mobile communication system according to claim 1, wherein the base station transmits the coverage information to the network device triggered by starting operation of the predetermined cell.   The mobile communication system according to claim 5, wherein the base station transmits the coverage information to the network device in response to a request from the network device. A user terminal residing in any one of the plurality of cells;
A base station that manages the cell in which the user terminal is located, and
The mobile communication system according to claim 1, wherein the base station receives the coverage information from the user terminal and transmits the received coverage information to the network device. In response to receiving the first request from the network device, the base station transmits a transmission request for the coverage information to the user terminal,
The mobile communication system according to claim 8, wherein the user terminal transmits the coverage information to the base station in response to reception of the transmission request for the coverage information.   The mobile communication system according to claim 8, wherein the base station transmits the coverage information received from the user terminal to the network device in response to reception of a second request from the network device. . The user terminal has acquired timing information for adjusting the transmission timing of the user terminal,
The mobile communication system according to claim 8, wherein the user terminal transmits the timing information acquired when connecting to the base station to the base station as the coverage information. A base station that manages any one of the plurality of cells;
2. The mobile communication system according to claim 1, wherein, when the MBSFN reference signal resource amount is changed, the network device notifies the base station of information regarding the change of the MBSFN reference signal resource amount. .   The mobile communication system according to claim 1, wherein the network device is a macro base station that manages a macro cell that overlaps each of the plurality of the network devices. Further comprising a user terminal residing in the cell managed by the base station,
The mobile communication system according to claim 12, wherein the macro base station broadcasts information related to the change of the MBSFN reference signal resource amount to the user terminal. A network device used in a mobile communication system in which an MBSFN area is configured by a plurality of cells that transmit MBSFN (MBMS Single Frequency Network) reference signals,
A control unit configured to set an MBSFN reference signal resource amount that is an amount of time / frequency resources of the MBSFN reference signal in the frequency direction;
The said control part sets the said MBSFN reference signal resource amount based on the coverage information regarding each coverage size of these cells, The network apparatus characterized by the above-mentioned.

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