JP2014075741A - Radio communication system, base station, mobile station, communication control method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide data bearer establishment procedure suitable for use of a Low Power Node (LPN).SOLUTION: A first base station (1) determines which cell is to be used between a first cell (10) which is operated by a first base station (1) for transferring user data of a mobile station (3) and a second cell (20) which is operated by a second base station (2), according to whether or not predetermined conditions are satisfied. When using the second cell (20), the first base station (1) transmits to a core network (4) a setting request of a bearer for transferring the user data through the second cell (20) between the core network (4) and the mobile station (3).

Description

  The present invention relates to wireless communication systems, and more particularly to establishment of data bearers.

  In Long Term Evolution (LTE) Release 12 in the 3rdGenelation Partnership Project (3GPP), "local area enhancement" or "to accommodate local huge traffic, improve throughput, and use high frequency bands efficiently" "Small cell enhancement" is one of the agenda items (see Non-Patent Document 1). In local area enhancement or small cell enhancement, a low-power node (LPN) that forms a small cell is used.

  Furthermore, C / U-plane split scenarios have been proposed for small cell enhancement. In C / U-plane split, the macro cell provides a control plane (for example, Radio Resource Control (RRC) connection and Non-Access Stratum (NAS) message transfer) to the mobile station (User Equipment (UE)). The cell provides a user plane for the UE. Looking at a specific introduction example for the control plane (C-plane), the macro cell can maintain a good connection with the UE and support the mobility of the UE with a wide coverage using a low frequency band. On the other hand, looking at the user plane (U-plane), the small cell can provide high local throughput to the UE by using a wide bandwidth in a high frequency band.

  In the C / U-plane split scenario, the small cell is an existing cell-specific signal / channel, such as Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), Cell-specific Reference Signal (CRS), Master Information Block ( It is assumed that transmission of MIB) and System Information Block (SIB) is not required. Therefore, such a new small cell may be called a phantom cell. In addition, a base station (eNB) or LPN that provides a small cell may be called a Phantom eNodeB (PhNB).

3GPP RWS-120010, NTT DOCOMO, "Requirements, Candidate Solutions & Technology Roadmap for LTE Rel-12 Onward", 3GPP TSG RAN Workshop on Rel-12 and Onwards Ljubljana, Slovenia, 11-12 June 2012

  When using LPN and small cell, it is expected that UE handover / data bearer switching to another cell will frequently occur due to small coverage of small cell. Then, when a data bearer for transferring user data is set to LPN, some requirements such as latency, throughput, or data loss may not be satisfied. This means that the data bearer set in the LPN is not suitable for a specific service (for example, Voice over IP (VoIP), online gaming, etc.) that requires low latency or small data loss. In addition, other factors such as LPN load, LPN radio quality, UE mobility, and the like may also be an obstacle when using LPN.

  One of the objects of the present invention is to provide a radio communication system, a base station, a communication control method, and a program in which a data bearer establishment procedure suitable for use of a low power node (LPN) is implemented.

  In the first aspect, the wireless communication system includes a first base station that operates the first cell, a second base station that operates the second cell, a core network, and a mobile station. The core network includes a mobility management device and a data relay device. Whether the first base station uses the first cell or the second cell for transferring user data of the mobile station, depending on whether a predetermined condition is satisfied or not Is configured to determine. Furthermore, when the first base station uses the second cell, the first base station bears a bearer for transferring the user data between the data relay apparatus and the mobile station via the second cell. Is transmitted to the mobility management apparatus.

  In the second aspect, the first base station includes a radio communication unit that operates the first cell, and a control unit. The control unit uses either the first cell or the second cell operated by the second base station for transferring user data of the mobile station depending on whether or not a predetermined condition is satisfied. Is configured to determine what to use. Further, when the second cell is used, the control unit sends a bearer setting request for transferring the user data between the core network and the mobile station via the second cell. It is configured to transmit to the core network.

  In the third aspect, the mobile station is used in combination with the wireless communication system according to the first aspect described above, and includes a wireless communication unit and a control unit. The control unit receives setting information for establishing a data radio bearer with the second base station from the first base station, receives user data using the second cell, or The wireless communication unit is configured to control transmission.

In the fourth aspect, the communication control method in the first base station that operates the first cell is:
(A) Depending on whether a predetermined condition is satisfied, either the first cell or the second cell operated by the second base station is used for transferring user data of the mobile station And (b) a bearer for transferring the user data between the core network and the mobile station via the second cell when using the second cell. Sending a configuration request to the core network;
including.

  In the fifth aspect, the program includes a group of instructions for causing a computer to perform the communication control method according to the fourth aspect described above.

  According to the above-described aspect, it is possible to provide a wireless communication system, a base station, a communication control method, and a program that implement a data bearer establishment procedure suitable for use of a Low Power Node (LPN).

It is a figure which shows the structural example of the radio | wireless communications system (e.g. LTE system) which concerns on 1st Embodiment. It is a figure which shows an example of the bearer architecture in the radio | wireless communications system which concerns on 1st Embodiment. It is a figure which shows the structural example of the 1st base station (e.g. MeNB) which concerns on 1st Embodiment. It is a figure which shows the structural example of the 2nd base station (e.g. LPN) which concerns on 1st Embodiment. It is a figure which shows the structural example of the mobile station (e.g. UE) which concerns on 1st Embodiment. It is a figure which shows the structural example of the mobility management apparatus (e.g. MME) which concerns on 1st Embodiment. It is a figure which shows the structural example of the data relay apparatus (e.g. S-GW) which concerns on 1st Embodiment. It is a sequence diagram which shows the establishment procedure of the data bearer which concerns on 1st Embodiment. It is a sequence diagram which shows the establishment procedure of the data bearer which concerns on 1st Embodiment. It is a flowchart which shows the operation example of the 1st base station (e.g. MeNB) which concerns on 1st Embodiment. It is a flowchart which shows the operation example of the 2nd base station (e.g. LPN) which concerns on 1st Embodiment. It is a flowchart which shows the operation example of the mobile station (e.g. UE) which concerns on 1st Embodiment. It is a flowchart which shows the operation example of the mobility management apparatus (e.g. MME) which concerns on 1st Embodiment. It is a flowchart which shows the operation example of the data relay apparatus (e.g. S-GW) which concerns on 1st Embodiment. It is a figure which shows an example of the bearer architecture in the radio | wireless communications system which concerns on 2nd Embodiment. It is a sequence diagram which shows the establishment procedure of the data bearer which concerns on 2nd Embodiment. It is a sequence diagram which shows the establishment procedure of the data bearer which concerns on 2nd Embodiment. It is a figure which shows an example of the bearer architecture in the radio | wireless communications system which concerns on 3rd Embodiment.

  Hereinafter, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted as necessary for clarification of the description.

<First Embodiment>
FIG. 1 shows a configuration example of a wireless communication system according to the present embodiment. The wireless communication system according to the present embodiment includes a first base station 1, a second base station 2, a mobile station 3, and a core network 4. The base stations 1 and 2 operate the first cell 10 and the second cell 20, respectively. Here, the cell 20 has a smaller coverage than the cell 10. The cell 10 and the cell 20 are typically operated in different frequency bands (for example, a 2 GHz band and a 3.5 GHz band). The core network 4 includes a mobility management device 5 and a data relay device 6. Hereinafter, for ease of explanation, a case where the radio communication system according to the present embodiment is an LTE system will be described as an example. Here, the first base station 1 is MeNB, the second base station 2 is LPN, the mobile station 3 is UE, the core network 4 is Evolved Packet Core (EPC), the mobility management device 5 is Mobility Management Entity (MME), The data relay device 6 corresponds to a Serving Gateway (S-GW).

  The radio communication system according to the present embodiment applies C / U-plane split to the cell 20. That is, the LPN 2 provides a U-plane service to the UE 3 in the cell 20. In other words, the LPN 2 establishes a data radio bearer (Data Radio bearer (DRB)) with the UE 3 and transfers user data of the UE 3. MeNB1 provides C-plane service in cell 10 to UE3 that establishes LPB2 and DRB. In other words, MeNB 1 establishes a signaling radio bearer (Signaling Radio Bearer (SRB)) with UE 3, RRC signaling for establishing and modifying DRB with LPN 2 in cell 20, and EPC 4 NAS message transfer between UE3 and UE3. Further, the MeNB 1 uses the master information (for example, the system bandwidth, the number of transmission antennas, etc.) and the system information (for example, parameters related to the DRB of the cell 20) regarding the cell 20 of the LPN 2 as the downlink channel (for example, Physical Broadcast Channel). (PBCH) or Physical Downlink Shared Channel (PDSCH)) may be used for transmission.

  In addition, MeNB1 does not need to bear all the C-plane services regarding UE3. For example, the LPN 2 may control layer 1 (physical layer) and layer 2 (Media Access Control (MAC) sublayer and Radio Link Control (RLC) sublayer). Specifically, the LPN 2 uses an uplink control channel (for example, Physical Uplink Control Channel (PUCCH)) or an uplink data channel (for example, Physical Uplink Shared Channel (PUSCH)) to perform a layer 1 / layer 2 control signal. (For example, Hybrid Automatic Repeat Request (H-ARQ) ACK, Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), and Rank Indicator (RI)) may be received. The LPN may transmit downlink scheduling information, ACK / NACK for uplink transmission, and the like to the UE 3 using a downlink control channel (for example, Physical Downlink Control Channel (PDCCH)).

  The EPC 4 is a network managed mainly by an operator who provides a mobile communication service. The EPC4 has a control plane (C-plane) function for performing mobility management (for example, location registration, location update) and bearer management (for example, bearer establishment, bearer configuration change, bearer release), etc., and MeNB1 and LPN2 It has a user plane (U-plane) function for transferring user data of UE3 to an external network (not shown). MME5 bears the C-plane function by EPC. The S-GW 6 is responsible for the U-plane function in EPC. The S-GW 6 is arranged at the boundary with a radio access network (Radio Access Network (RAN)) including the MeNB 1 and the LPN 2.

  Next, a specific example of the bearer architecture according to the present embodiment will be described with reference to FIG. FIG. 2 shows an example of a bearer architecture related to user data transfer in cell 20. The radio bearer has already been described. That is, MeNB1 establishes an SRB with UE3, CRCplane services such as RRC signaling for establishing and modifying DRB in cell 20, and NAS message transfer between EPC4 and UE3 I will provide a. Moreover, LPN2 establishes DRB between UE3 and transmits / receives user data of UE3.

  Next, the bearer between EPC4 and MeNB1 and LPN2 is demonstrated. A signaling bearer with the EPC 4 (that is, an S1 signaling bearer using the S1-MME interface) is established between the MME 5 and the MeNB1. MeNB1 establishes an S1 signaling bearer with MME5, and transmits and receives an S1 Application Protocol (S1-AP) message with MME5. On the other hand, the data bearer with the EPC 4 (that is, the S1 bearer using the S1-U interface) is established between the S-GW 6 and the LPN 2. LPN 2 establishes an S1 bearer with S-GW 6 and transmits / receives user data of UE 3 to / from S-GW 6.

  Furthermore, MeNB1 establishes a signaling bearer with LPN2. The signaling bearer between MeNB1 and LPN2 is established using, for example, the X2 interface. The X2 interface is an interface between eNBs. Note that it is possible that LPN3 is defined as a new node and a new interface different from the X2 interface is defined between eNB and LPN. In this case, the signaling bearer between MeNB1 and LPN2 may be established using this new interlace. This new interface is referred to herein as an X3 interface. The MeNB 1 uses the bearer setting information (hereinafter referred to as E-UTRAN Radio Access Bearer (E-RAB) setting information) necessary for establishing the S1 bearer with the S-GW 6 and the DRB with the UE 3 in the LPN 2 as X2. It is configured to transmit to LPN2 via the / X3 signaling bearer. The E-RAB means a radio access bearer including an S1 bearer and a DRB.

  According to the bearer architecture described above, the LPN 2 does not need an S1 signaling bearer with the MME 5, and can set an S1 bearer and a DRB based on E-RAB setting information given from the MeNB1. Further, in the bearer architecture described above, the termination point of the S1 bearer (S1-U bearer) is different from the termination point of the S1 signaling bearer. That is, not MeNB1, but LPN2 terminates the S1 bearer. That is, in the architecture of FIG. 2, the C / U plane is separated not only in the signaling within the RAN but also at the interface between the EPC 4 and the RAN. Thereby, MeNB1 only needs to perform signaling for establishing DRB and S1 bearer required for UE3 to transmit and receive user data via cell 20 and LPN2. In other words, the MeNB 1 does not need to terminate the S1 bearer (that is, the GPRS Tunneling Protocol (GTP) tunnel) for the communication of the UE 3 via the cell 20, and forwards the user data packet between the S1 bearer and the DRB. There is no need to do any processing. These processes are performed by LPN2. Therefore, the processing load of MeNB1 can be reduced.

  Below, on the assumption of the bearer architecture example shown in FIG. 2, a configuration example of each device and a specific example of a data bearer establishment procedure will be described. However, it should be noted that the bearer architecture shown in FIG. 2 is only an example. For example, an S1 bearer GTP tunnel packet terminated at LPN 2 may be transferred between S-GW 6 and LPN 2 via MeNB 1. Moreover, the S1 bearer for transferring the user packet of UE3 via the cell 20 and LPN2 may be terminated not by LPN2 but by MeNB1. Some examples of these other bearer architectures are described in the second and third embodiments described below.

  A configuration example of MeNB1, LPN2, UE3, MME5, and S-GW6 according to the present embodiment will be described. FIG. 3 is a block diagram showing a configuration example of MeNB1. The wireless communication part 11 receives the uplink signal (uplink signal) transmitted from UE3 via an antenna. The reception data processing unit 13 restores the received uplink signal. The obtained received data is transferred to another network node such as the MME 5 or the S-GW 6 via the communication unit 14. For example, uplink user data received from the UE 3 in the cell 10 is transferred to the S-GW 6. Moreover, NAS data among the control data received from UE3 is transferred to MME5. Further, the reception data processing unit 13 receives control data transmitted to the LPN 2 or MME 5 from the control unit 15 and transmits it to the LPN 2 or MME 5 via the communication unit 14.

  The transmission data processing unit 12 acquires user data addressed to the UE 3 from the communication unit 14, and performs error correction coding, rate matching, interleaving, and the like to generate a transport channel. Further, the transmission data processing unit 12 adds control information to the data sequence of the transport channel to generate a transmission symbol sequence. The radio communication unit 11 generates a downlink signal by performing various processes such as carrier wave modulation, frequency conversion, and signal amplification based on the transmission symbol sequence, and transmits this to the UE 3. Further, the transmission data processing unit 12 receives control data transmitted to the UE 3 from the control unit 15 and transmits it to the UE 3 via the wireless communication unit 11.

  The control unit 15 determines whether to use the cell 10 or the cell 20 for the transfer of user data related to the UE 3, and establishes the S1 bearer and the DRB via the LPN 2 in response to the use of the cell 20 being determined. Configure to require. Specifically, the control unit 15 signals the MME 5, the LPN 2 and the UE 3 via the signaling bearer so that the UE 3 can receive or transmit user data in the cell 20 operated by the LPN 2. Specifically, the control unit 15 transmits an E-RAB or S1 bearer establishment request to the MME 5 via the S1 signaling bearer. Furthermore, the control unit 15 transmits E-RAB setting information necessary for establishing the S1 bearer and DRB in the LPN 2 to the LPN 2 via the X2 / X3 signaling bearer. Furthermore, the control unit 15 transmits DRB setting information necessary for establishing the DRB in the cell 20 in the UE 3 to the UE 3 via the SRB in the cell 10.

  FIG. 4 is a block diagram showing a configuration example of LPN2. The functions and operations of the wireless communication unit 21, the transmission data processing unit 22, the reception data processing unit 23, and the communication unit 24 shown in FIG. 6 correspond to the corresponding elements of the base station 1 shown in FIG. The same as the unit 11, the transmission data processing unit 12, the reception data processing unit 13, and the communication unit 14.

  The control unit 25 of LPN2 receives the E-RAB setting information from MeNB1 (control unit 15) via the X2 / X3 signaling bearer, and the S1 bearer with S-GW6 and the SRB with UE3 according to the E-RAB setting information. Set.

  FIG. 5 is a block diagram illustrating a configuration example of the UE 3. The wireless communication unit 31 can communicate with both the cell 10 and the cell 20. Further, the radio communication unit 31 may support carrier aggregation of a plurality of cells operated by different eNBs. In this case, the wireless communication unit 31 can simultaneously use the plurality of cells 10 and 20 for transmitting or receiving user data. The radio communication unit 31 receives a downlink signal from the eNB 1 or LPN 2 or both via the antenna. The reception data processing unit 32 restores the reception data from the received downlink signal and sends it to the data control unit 33. The data control unit 33 uses the received data according to the purpose. Also, the transmission data processing unit 34 and the wireless communication unit 31 generate an uplink signal using the transmission data supplied from the data control unit 33 and transmit the uplink signal to the eNB 1 or the LPN 2 or both.

  The control unit 35 of the UE 3 controls the radio communication unit 31 so as to establish an SRB in the cell 10 with the MeNB 1. And the control part 35 receives the DBB setting information for establishing DRB between LPN2 from MeNB1, and controls the radio | wireless communication part 31 to receive or transmit user data using the cell 20. FIG. Thereby, U3 can communicate via LPB between LPN2 based on signaling with MeNB1.

  FIG. 6 is a block diagram illustrating a configuration example of the MME 5. The communication unit 51 communicates with the MeNB 1 and the S-GW 6. The bearer setting control unit 52 communicates with the MeNB 1 and the S-GW 6 via the communication unit 51, and controls the setting of the signaling bearer or the data bearer in these devices. Specifically, the bearer setting control unit 52 requests the S-GW 6 to set the S1 bearer in response to the data bearer (E-RAB or S1 bearer) setting request from the base station 1 or 2, and -The bearer setting information regarding RAB or S1 bearer is transmitted to MeNB1.

  FIG. 7 is a block diagram illustrating a configuration example of the S-GW 6. The communication unit 61 establishes an S1 bearer with the LPN 2 and transmits or receives user data to and from the LPN 2 via the S1 bearer. The communication unit 61 may establish an S1 bearer with the MeNB 1 in order to receive or transmit user data via the cell 10 by the UE 3. The communication unit 64 sets up an S5 / S8 bearer with the Packet Data Network Gateway (P-GW) in the EPC 4 and transmits / receives user data to / from other data relay apparatuses.

  The transmission data processing unit 62 receives downlink user data addressed to the UE 3 from the communication unit 64, and forwards the downlink user data to the S1 bearer based on the correspondence relationship between the upstream side, the S5 / S8 bearer, and the downstream S1 bearer. To do. The reception data processing unit 63 receives the uplink user data from the communication unit 61, and forwards the uplink user data to the S5 / S8 bearer based on the correspondence relationship between the S5 / S8 bearer and the S1 bearer.

  The bearer control unit 65 communicates with the MME 5 and sets an S1 bearer between the LPN 2 and the communication unit 61 according to the control of the MME 5.

  Subsequently, a procedure for establishing a data bearer according to the present embodiment will be described. MeNB1 which concerns on this embodiment determines which of cell 10 and cell 20 is used for the transfer of the user data regarding UE3, and according to having determined use of cell 20, S1 bearer and DRB which pass LPN2 Is configured to transmit the establishment request to the MME 5. MeNB1 determines use of the cell 20 when a predetermined condition is satisfied. The predetermined condition includes, for example, at least one of bearer priority, delay amount allowed for user data of UE3, load of LPN2, wireless quality of LPN2, positional relationship between UE3 and LPN2, and mobility of UE3 One thing. Below, the specific example of the conditions for determining use of the cell 20 is demonstrated.

  In the first example, the predetermined condition relates to bearer priority. MeNB1 decides to use cell 10 of MeNB1 for the transfer of user data of UE3 when the bearer priority is higher than the reference value, and LPN2 for the transfer of user data of UE3 when the bearer priority is lower than the reference value You may decide to use the cell 20 of this.

  In the second example, the predetermined condition relates to a delay amount allowed for the user data of UE3. The MeNB1 decides to use the cell 10 for transferring user data of the UE3 when the allowable delay amount is smaller than the reference value, and transfers the user data of the UE3 when the allowable delay amount is larger than the reference value. It may be decided to use the cell 20.

  In the third example, the predetermined condition relates to the load of LPN2. MeNB1 decides to use cell 10 for transferring user data of UE3 when the load of LPN2 is larger than the reference value, and uses cell 20 for transferring user data of UE3 when the load of LPN2 is smaller than the reference value You may decide to do that. The load of the LPN 2 may be, for example, a resource usage amount, a resource usage rate, or a user data traffic amount. Moreover, MeNB1 may collect the load of LPN2 from LPN2 periodically or aperiodically. Moreover, LPN2 may notify MeNB1 of the load of LPN2 periodically, and may notify MeNB1 aperiodically according to the load having exceeded the reference value.

  In the fourth example, the predetermined condition relates to the radio quality of LPN2. MeNB1 decides to use cell 10 for transferring user data of UE3 when the radio quality of LPN2 is lower than the reference value, and cell 20 for transferring user data of UE3 when the radio quality of LPN2 is higher than the reference value. You may decide to use The radio quality of LPN2 may be, for example, Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ) of LPN2. The radio quality of LPN2 may be measured by UE3 and reported from UE3 to MeNB1.

  In the fifth example, the predetermined condition relates to the positional relationship between UE3 and LPN2. MeNB1 decides to use the cell 10 for transferring user data of UE3 when the evaluation value indicating the distance between LPN2 and UE3 is larger than the reference value, and when the evaluation value is smaller than the reference value, the user of UE3 It may be decided to use the cell 20 for data transfer. In this case, MeNB1 should just manage the positional information on LPN2, and should acquire the positional information on UE3. The position information of LPN 2 and UE 3 may be, for example, Global Positioning System (GPS) information.

  In the sixth example, the predetermined condition relates to the mobility of UE3. MeNB1 decides to use cell 10 for the transfer of user data of UE3 when the evaluation value indicating the mobility of UE3 is higher than the reference value, and transfers the user data of UE3 when the evaluation value is lower than the reference value The cell 20 may be determined to be used. The evaluation value indicating the mobility of UE3 may be an average moving speed calculated from position information (for example, GPS information) of UE3. Further, the evaluation value indicating the moving speed of UE3 may be a cell stay time of UE3, a handover frequency of UE3, or the like. The cell residence time of UE3 and the handover frequency of UE3 are related to the mobility of UE3. That is, when UE3 has high mobility, it is considered that the average cell stay time of UE3 is shortened and the handover frequency of UE3 is increased.

  8 and 9 are sequence diagrams illustrating an example of a procedure for establishing a data bearer according to the present embodiment. In step S101, MeNB1 establishes S1 connection linked | related with UE3 between MME5 for UE3 which belongs to the cell 10. FIG. That is, MeNB1 establishes an S1 signaling bearer with MME5 in the S1-MME interface. In step S102, the MeNB 1 establishes an RRC connection with the UE 3 in the cell 10. In step S103, MeNB1 determines whether to set the data bearer for UE3 to MeNB1 (cell 10) or LPN2 (cell 20). Specific examples of conditions for determining the LPN2 cell 20 are as described above.

  Step S104A or S104B is alternatively executed according to the determination in step S103. That is, when the use of the cell 20 (secondary cell) is determined, the MeNB 1 requests the MME 5 to establish the S1 bearer and DRB via the LPN 2 and signals the UE 3 and the LPN 2. As a result, the S1 bearer and the DRB that pass through the LPN 2 are established. UE3 transmits / receives user data via cell 20 of LPN2 (step S804A). On the other hand, when it is determined to use the cell 10 (primary cell), the MeNB 1 requests the MME 5 to establish the S1 bearer and the DRB via the MeNB 1. Thereby, the S1 bearer and DRB that pass through MeNB1 are established. UE3 transmits / receives user data via the cell 10 of MeNB1 (step S804B).

  The sequence diagram of FIG. 9 shows a specific example of step S104A shown in FIG. In steps S1041 to S1045 of FIG. 9, DRB and S1 bearer establishment processing via LPN2 is performed. In step S1041, MeNB1 transmits the establishment request | requirement of E-RAB via LPN2 for UE3 to MME5. The MME 5 that has received the request starts an S1 bearer setting procedure. Specifically, the S-GW 6 is requested to set up an S1 bearer with the LPN 2. The S-GW 6 sets up an S1 bearer with the LPN 2 and sends a response including the S1 bearer context (for example, the address of the S-GW 6 on the U-plane and a tunnel endpoint identifier (Tunnel Endpoint Identifier (TEID)) to the MME 5. TEID indicates an end point on the S-GW 6 side of the GTP tunnel as the S1 bearer, and the MME 5 transmits E-RAB setting information including the S1 bearer context to the MeNB1.

  In steps S1042 and S1043, MeNB1 transmits E-RAB setting information to LPN2 via the X2 / X3 signaling bearer. The E-RAB setting information includes S1 bearer setting information and DRB setting information. LPN2 sets S1 bearer and DRB according to E-RAB setting information. The S1 bearer setting information includes information necessary for establishing the S1 bearer with the S-GW 6. The S1 bearer setting information includes, for example, E-RAB ID, Quality Class Indicator (QCI), IP address of S-GW 6, TEID of S-GW 6, security key, Temporary Mobile Subscriber Identity (TMSI) and the like. Also, the DRB setting information includes setting information necessary for establishing a DRB with UE3. The DRB setting information includes, for example, E-RAB ID, Quality Class Indicator (QCI), and physical layer and MAC sublayer setting information.

  In Step S1044, MeNB1 transmits a RRC reconfiguration message to UE3 using the SRB of cell 10. The message includes DRB setting information in the cell 20. UE3 sets DRB according to the setting information of DRB.

  In step S1045, MeNB1 transmits a message (CREATE BEARER RESPONSE) indicating the completion of E-RAB setting to MME5. The message includes setting information on the LPN2 side regarding the S1 bearer (for example, the address and TEID of LPN2). The MME 5 transmits a message including the address of LPN 2 and the TEID to the S-GW 6. The S-GW 6 updates the S1 bearer setting with the address and TEID of LPN 2 received from the MME 5.

  Through the processes in steps S1041 to S1045 described above, an E-RAB that passes through LPN2 is set between UE3 and S-GW5. In step S1046, UE3 receives or transmits user data via cell 20 and LPN2.

  Step S105 in FIG. 9 shows an example of the update procedure of the secondary cell (that is, the cell 20). For example, MeNB1 passes LPN2 based on the usage status (total traffic volume, number of connected UEs, etc.) of cell 20, traffic volume (user data volume) for each UE3 using cell 20, or a combination thereof. The E-RAB (that is, DRB and S1 bearer) for each UE 3 may be deactivated or the cell 20 may be stopped. For example, MeNB1 may deactivate E-RAB of the said UE3, when the communication of UE3 is complete | finished or when the traffic amount falls. For example, when the load on the own cell 10 decreases, the MeNB 1 may deactivate all the E-RABs that pass through the LPN 2 and stop using the cell 20. In the specific example shown in FIG. 4, MeNB1 receives a status report from LPN2 (step S1051). The status report indicates the load of the cell 20 (for example, the total traffic amount, the radio resource usage amount, the radio resource usage rate, or the number of connected UEs). In step S1052, MeNB1 requests the update (modification) of the cell 20 based on the status report (SCell Modify Request).

  FIG. 10 is a flowchart illustrating an operation example of the MeNB 1. In step S201, MeNB1 (control part 15) determines establishment of the data bearer in LPN2 (or activation of the cell 20 of LPN2). In step S202, MeNB1 requests MME5 to establish E-RAB via LPN2. In step S203, MeNB1 determines reception of E-RAB setting information from MME5. When the E-RAB setting information is received (YES in step S203), the MeNB 1 transmits the E-RAB setting information to the LPN 2. In step S205, MeNB1 determines reception from LPN2 of a notification indicating completion of setting of E-RAB (that is, S1 bearer and DRB). When the E-RAB setting completion notification is received from the LPN 2 (YES in step S205), the MeNB 1 notifies the UE 3 of the DRB setting information in the cell 10. In step S207, MeNB1 determines reception from UE3 of the notification which shows the completion of DRB setting. When the DRB setting completion notification is received from the UE 3 (YES in step S207), the MeNB 1 notifies the MME 5 of the completion of E-RAB setting.

  FIG. 11 is a flowchart showing an operation example of LPN2. In step S301, LPN2 (control part 25) determines whether E-RAB setting information was received from MeNB1. When the E-RAB setting information is received (YES in step S301), the LPN 2 sets the S1 bearer with the S-GW 6 and the DRB with the UE 3 according to the E-RAB setting information (steps S302 and S302). S303). In step S304, LPN2 notifies MeNB1 of completion of E-RAB setting.

  FIG. 12 is a flowchart illustrating an operation example of the UE 3. In step S401, UE3 (control part 35) receives DRB setting information from MeNB1. In step S402, UE3 sets DRB with LPN2 in the cell 20 according to DRB setting information.

  FIG. 13 is a flowchart showing an operation example of the MME 5. In step S501, MME5 (bearer setting control part 52) determines whether the E-RAB setting request | requirement was received from MeNB1. When the E-RAB setting request is received (YES in step S501), the MME 5 generates S1 bearer setting information related to LPN2, and notifies this to the S-GW 6 (steps S502 and S503). In step S504, the MME 5 determines whether a bearer setting completion notification is received from the S-GW 6. When the bearer setting completion notification is received (YES in step S504), the MME 5 notifies the ENBA setting information to the MeNB 1 (step S505). In step S506, the MME 5 determines whether an E-RAB setting completion notification is received from the MeNB1. When the E-RAB setting completion notification is received (YES in step S506), the MME 5 notifies the E-RAB setting completion to the S-GW 6 (step S507). The E-RAB setting completion notification to the S-GW 6 includes LPN2 side setting information (for example, the address and TEID of the LPN2) regarding the S1 bearer between the LPN2 and the S-GW6.

  FIG. 14 is a flowchart showing an operation example of the S-GW 6. In step S601, the S-GW 6 (bearer control unit 65) determines whether the S1 bearer setting information is received from the MME 5. When the S1 bearer setting information is received (YES in step S601), the S-GW 6 sets an S1 bearer with the LPN 2 according to the S1 bearer setting information (step S602). In step S603, the S-GW 6 notifies the MME 5 of the completion of setting of the S1 bearer. The notification includes setting information on the S-GW 6 side regarding the S1 bearer with the LPN 2 (for example, the address and TEID of the S-GW 6). In step S604, the S-GW 6 determines whether an E-RAB setting completion notification from the MME 5 has been received. When the E-RAB setting completion notification is received (YES in step S604), the S-GW 6 updates (corrects) the setting of the S1 bearer with the LPN 2 in accordance with the E-RAB setting completion notification.

<Second Embodiment>
In this embodiment, a modified example of the bearer architecture described in the first embodiment will be described. A configuration example of the wireless communication system according to the present embodiment may be the same as that in FIG.

  In the bearer architecture of FIG. 2 described in the first embodiment, the S1 bearer for UE3 communicating in the cell 20 is terminated in the LPN2. The S1 bearer is a GTP tunnel, and user data (data packet) is encapsulated in a GTP tunnel packet transmitted / received between the S-GW 6 and the LPN 2. For example, a GTP tunnel packet encapsulating downlink user data reaches LPN 2 by being routed and forwarded by a router disposed between S-GW 6 and LPN 2. Therefore, typically, the GTP tunnel packet is transferred without going through MeNB1. In this case, since MeNB1 does not need to perform termination processing of the S1 bearer, the processing load of MeNB1 can be reduced. Further, since the GTP tunnel packet does not flow through the X2 / X3 interface between MeNB1 and LPN2, performance requirements regarding the capacity and delay of the X2 / X3 interface are alleviated. For example, a non-optical fiber line (for example, a wireless line) can be used for the X2 / X3 interface.

  On the other hand, the bearer architecture described below defines the routing of GTP tunnel packets in detail. That is, in this embodiment, a GTP tunnel packet encapsulating user data is transferred between S-GW 6 and LPN 2 via MeNB 1. The MeNB 1 functions as a router (for example, Internet Protocol (IP) router), and may route and forward the GTP tunnel packet. Routing of the GTP tunnel packet via MeNB1 can be realized by setting the routing table of S-GW6, LPN2, and MeNB1.

  One point to note is that MeNB1 does not need to terminate the S1 bearer. MeNB1 should just operate | move as a router which forwards a GTP tunnel packet, and does not need to perform the decapsulation process for taking out a user packet. Therefore, an increase in the processing load of MeNB1 accompanying the GTP tunnel termination does not occur.

  Another noteworthy point is that MeNB1 can observe GTP tunnel packets. For example, MeNB1 can observe the traffic volume of GTP tunnel packets to be transferred. By observing the traffic volume of the GTP tunnel packet, MeNB1 can autonomously estimate the load of LPN2 or the load of cell 20. Therefore, the MeNB 1 of this embodiment can determine whether the E-RAB or the cell 20 is deactivated via the LPN 2 (step S105 in FIG. 8) based on the traffic volume of the GTP tunnel packet observed by itself. it can.

  FIG. 15 is a diagram illustrating an example of a bearer architecture according to the present embodiment. In the example of FIG. 15, MeNB1 and LPN2 set up a tunnel 70 (for example, a GTP tunnel) at the X2 / X3 interface. The MeNB 1 further encapsulates the GTP tunnel packet encapsulating the user data in the S1 bearer between the S-GW 6 and the LPN 2 and transfers it using the tunnel 70. The tunnel 70 may not be set. That is, MeNB1 may transfer the GTP tunnel packet as it is without further encapsulating the GTP tunnel packet.

  16 and 17 are sequence diagrams illustrating an example of a procedure for establishing a data bearer according to the present embodiment. As is clear from comparison between FIGS. 8 and 9 and FIGS. 16 and 17, the bearer establishment procedure in this embodiment is the same as the example shown in the first embodiment. This is because the termination points of the S1 bearer are S-GW 6 and LPN 2 as in the example (FIG. 2) shown in the first embodiment. Therefore, the processes in steps S101 to S103 and S104B in FIG. 16 are the same as steps S101 to S103 and S104B in FIG. In Step S702 of FIG. 16, MeNB1 and LPN2 establish a tunnel 70 in the X2 / X3 interface. However, as described above, the tunnel 70 need not be established.

  A specific example of step S704A in FIG. 16 is shown in FIG. The processing in steps S1041 to S1045 of FIG. 17 is the same as S1041 to S1045 of FIG. In step S7046A in FIG. 17, the GTP tunnel packet between S-GW 6 and LPN 2 is transferred via MeNB 1. In this example, the GTP tunnel packet is transferred via the tunnel 70 in the X2 / X3 interface.

  Step S705 in FIG. 17 shows the update procedure of the secondary cell (that is, the cell 20), similarly to step S105 in FIG. For example, MeNB1 passes LPN2 based on the usage status (total traffic volume, number of connected UEs, etc.) of cell 20, traffic volume (user data volume) for each UE3 using cell 20, or a combination thereof. The E-RAB (that is, DRB and S1 bearer) for each UE 3 may be deactivated or the cell 20 may be stopped. In the specific example illustrated in FIG. 17, the MeNB 1 observes the traffic volume of the GTP tunnel packet transferred by itself (that is, the traffic volume of the cell 20) (step S77051). In step S7052, the MeNB 1 requests update (modification) of the cell 20 based on the observed traffic volume (SCell Modify Request).

<Third Embodiment>
In the present embodiment, another modification of the bearer architecture described in the first embodiment will be described. A configuration example of the wireless communication system according to the present embodiment may be the same as that in FIG. The first embodiment described above can also be applied to a wireless communication system having a bearer architecture different from the bearer architecture described in the first and second embodiments. For example, the first embodiment may be applied to a bearer architecture as shown in FIG. In the bearer architecture shown in FIG. 18, an S1 bearer for transferring user data of UE3 via cell 20 and LPN2 is terminated in MeNB1. User data obtained by terminating the S1 bearer (that is, Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU)) is a tunnel (X2 / X3 bearer) set on the X2 / X3 interface between MeNB1 and LPN2. Is transferred through.

  That is, in the first embodiment, the situation that is not suitable for the use of LPN2, the service characteristic, the characteristic of UE3, etc. are determined in MeNB1, and if it is not suitable for the use of LPN2, the cell 10 of MeNB1 is used. The processing and operation of MeNB1 does not depend on the bearer architecture.

<Other embodiments>
MeNB1 (control unit 15), LPN2 (control unit 25), UE3 (control unit 35), MME5 (bearer setting control unit 52), and S-GW6 (bearer control unit 65) described in the first to third embodiments. Any of the control methods related to bearer establishment by () may be realized using a semiconductor processing apparatus including an Application Specific Integrated Circuit (ASIC). These processes may be realized by causing a computer system including at least one processor (eg, a microprocessor, a micro processing unit (MPU), or a digital signal processor (DSP)) to execute a program. Specifically, one or a plurality of programs including a group of instructions for causing a computer system to execute the algorithm shown in the flowchart and the sequence diagram may be created and the programs may be supplied to the computer.

  This program can be stored using various types of non-transitory computer readable media and supplied to a computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W and semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)) are included. The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  Further, the first to third embodiments described above may be implemented in combination as appropriate.

  In addition, the first to third embodiments described above mainly describe the LTE system. However, these embodiments are applicable to wireless communication systems other than LTE systems, such as 3GPP UMTS (Universal Mobile Telecommunications System), 3GPP2 CDMA2000 system (1xRTT, HRPD (High Rate Packet Data)), GSM (Global System for Mobile Communications). It may be applied to a system or a WiMAX system.

  Furthermore, the above-described embodiment is merely an example relating to application of the technical idea obtained by the present inventors. That is, the technical idea is not limited to the above-described embodiment, and various changes can be made.

1 Base station (MeNB)
2 Base station (LPN)
3 Mobile station (UE)
4 Core network (EPC)
5 Mobility management equipment (MME)
6 Data relay device (S-GW)
15 Control unit 25 Control unit 35 Control unit 52 Bearer setting control unit 65 Bearer control unit 70 Tunnel

Claims (35)

A first base station operating a first cell;
A second base station operating a second cell;
A core network including a mobility management device and a data relay device;
A mobile station,
With
The first base station is
According to whether or not a predetermined condition is satisfied, it is determined which one of the first cell and the second cell is used for transferring user data of the mobile station;
When using the second cell, a bearer establishment request for transferring the user data between the data relay device and the mobile station via the second cell is transmitted to the mobility management device. Configured to
Wireless communication system.   The predetermined conditions are: bearer priority, amount of delay allowed for the user data, load of the second base station, radio quality of the second base station, and the mobile station and the second base station. The wireless communication system according to claim 1, wherein the wireless communication system relates to at least one of a positional relationship and mobility of the mobile station. The predetermined condition relates to the bearer priority,
The first base station determines to use the first cell for transferring the user data when the bearer priority is higher than a first reference value, and the bearer priority is set to the first Deciding to use the second cell for transferring the user data if lower than a reference value;
The wireless communication system according to claim 2. The predetermined condition relates to the allowable delay amount.
The first base station determines to use the first cell for transferring the user data when the allowable delay amount is smaller than a second reference value, and the allowable delay amount is Determining to use the second cell for transferring the user data if greater than a second reference value;
The wireless communication system according to claim 2 or 3. The predetermined condition relates to a load of the second base station,
The first base station determines to use the first cell for transferring the user data when the load of the second base station is greater than a third reference value, and the second base station Deciding to use the second cell for transferring the user data when the load of is less than the third reference value;
The radio | wireless communications system of any one of Claims 2-4. The predetermined condition relates to the radio quality of the second base station,
The first base station determines to use the first cell for transferring the user data when the radio quality is lower than a fourth reference value, and the radio quality is higher than the fourth reference value. Determining to use the second cell for transfer of the user data if high;
The radio | wireless communications system of any one of Claims 2-5. The predetermined condition relates to a positional relationship between the mobile station and the second base station,
The first base station uses the first cell for transferring the user data when an evaluation value representing a distance between the second base station and the mobile station is larger than a fifth reference value. And determining to use the second cell for transferring the user data when the evaluation value is smaller than the fifth reference value.
The radio | wireless communications system of any one of Claims 2-6. The predetermined condition relates to the mobility of the mobile station,
The first base station determines to use the first cell for transferring the user data when an evaluation value representing mobility of the mobile station is higher than a sixth reference value, and the evaluation value is Deciding to use the second cell for transferring the user data if lower than the sixth reference value;
The radio | wireless communications system of any one of Claims 2-7.   The bearer includes a data bearer between the data relay device and the second base station, and a data radio bearer between the second base station and the mobile station in the second cell. The radio | wireless communications system of any one of -8.   The first base station is further configured to transmit configuration information required to establish the data bearer and the data radio bearer at the second base station to the second base station. Item 10. The wireless communication system according to Item 9.   The first base station is further configured to transmit configuration information required to configure the data radio bearer in the mobile station to the mobile station in the first cell. The wireless communication system described.   The mobile station is configured to transmit or receive the user data via the data radio bearer without setting up a signaling radio bearer with the second base station. The wireless communication system according to any one of the above. A wireless communication unit operating the first cell;
A control unit;
With
The controller is
Whether to use the first cell or the second cell operated by the second base station for transferring user data of the mobile station depending on whether or not a predetermined condition is satisfied Decide
When using the second cell, a bearer setting request for transferring the user data between the core network and the mobile station via the second cell is transmitted to the core network.
First base station.   The predetermined conditions are: bearer priority, amount of delay allowed for the user data, load of the second base station, radio quality of the second base station, and the mobile station and the second base station. The first base station according to claim 13, wherein the first base station relates to at least one of a positional relationship and mobility of the mobile station. The predetermined condition relates to the bearer priority,
The control unit determines to use the first cell for transferring the user data when the bearer priority is higher than a first reference value, and the bearer priority is higher than the first reference value. Determining to use the second cell for transferring the user data if low;
The first base station according to claim 14. The predetermined condition relates to the allowable delay amount.
The control unit determines to use the first cell for transferring the user data when the allowable delay amount is smaller than a second reference value, and the allowable delay amount is the second delay value. Determining to use the second cell for transferring the user data if greater than a reference value;
The first base station according to claim 14 or 15. The predetermined condition relates to a load of the second base station,
The control unit determines to use the first cell for transferring the user data when the load of the second base station is larger than a third reference value, and the load of the second base station is Deciding to use the second cell for transferring the user data if the third reference value is smaller than the third reference value;
The 1st base station of any one of Claims 14-16. The predetermined condition relates to the radio quality of the second base station,
The control unit determines to use the first cell for transferring the user data when the wireless quality is lower than a fourth reference value, and when the wireless quality is higher than the fourth reference value. Deciding to use the second cell for transferring the user data;
The 1st base station of any one of Claims 14-17. The predetermined condition relates to a positional relationship between the mobile station and the second base station,
The control unit determines to use the first cell for transferring the user data when an evaluation value representing a distance between the second base station and the mobile station is larger than a fifth reference value. Deciding to use the second cell for transferring the user data when the evaluation value is smaller than the fifth reference value;
The 1st base station of any one of Claims 14-18. The predetermined condition relates to the mobility of the mobile station,
The control unit determines to use the first cell for transferring the user data when an evaluation value representing mobility of the mobile station is higher than a sixth reference value, and the evaluation value is the sixth value. Determining to use the second cell for transferring the user data if the reference value is lower than
The 1st base station of any one of Claims 14-19.   The bearer includes a data bearer between the data relay apparatus in the core network and the second base station, and a data radio bearer between the second base station and the mobile station in the second cell. The first base station according to any one of claims 13 to 20.   The control unit is further configured to transmit configuration information required to establish the data bearer and the data radio bearer at the second base station to the second base station. The first base station described.   The control unit according to claim 22, wherein the control unit is further configured to transmit configuration information required to configure the data radio bearer in the mobile station to the mobile station in the first cell. 1 base station.   The first base station according to any one of claims 13 to 23, wherein the setting request is transmitted to a mobility management device in the core network. A mobile station used in combination with the wireless communication system according to any one of claims 1 to 12,
A wireless communication unit;
Receiving the setting information for establishing a data radio bearer with the second base station from the first base station, and receiving or transmitting user data using the second cell; A control unit for controlling the communication unit;
A mobile station comprising:   The mobile station according to claim 25, wherein the control unit controls transmission or reception of the user data via the data radio bearer without setting up a signaling radio bearer with the second base station. . A communication control method in a first base station that operates a first cell,
Whether to use the first cell or the second cell operated by the second base station for transferring user data of the mobile station depending on whether or not a predetermined condition is satisfied And determining a bearer setting request for transferring the user data between the core network and the mobile station via the second cell when using the second cell. Sending to
A communication control method comprising:   The predetermined conditions are: bearer priority, amount of delay allowed for the user data, load of the second base station, radio quality of the second base station, and the mobile station and the second base station. 28. The method of claim 27, relating to at least one of a positional relationship and mobility of the mobile station. The predetermined condition relates to the bearer priority,
The determining determines to use the first cell for transferring the user data when the bearer priority is higher than a first reference value, and the bearer priority is the first reference value. Deciding to use the second cell for transferring the user data if lower,
30. The method of claim 28. The predetermined condition relates to the allowable delay amount.
The determining determines to use the first cell for transferring the user data when the allowable delay amount is smaller than a second reference value, and the allowable delay amount is the second delay amount. Determining to use the second cell for transfer of the user data if greater than a reference value of
30. A method according to claim 28 or 29. The predetermined condition relates to a load of the second base station,
The determining determines to use the first cell for transferring the user data when the load of the second base station is greater than a third reference value, and the load of the second base station Determining to use the second cell for transferring the user data if is less than the third reference value;
31. A method according to any one of claims 28-30. The predetermined condition relates to the radio quality of the second base station,
The determining determines to use the first cell for transferring the user data when the radio quality is lower than a fourth reference value, and when the radio quality is higher than the fourth reference value Determining to use the second cell for transferring the user data,
32. A method according to any one of claims 28 to 31. The predetermined condition relates to a positional relationship between the mobile station and the second base station,
The determining determines to use the first cell for transferring the user data when an evaluation value representing a distance between the second base station and the mobile station is larger than a fifth reference value. And determining to use the second cell for transferring the user data when the evaluation value is smaller than the fifth reference value,
33. A method according to any one of claims 28 to 32. The predetermined condition relates to the mobility of the mobile station,
The determining determines to use the first cell for transferring the user data when an evaluation value indicating mobility of the mobile station is higher than a sixth reference value, and the evaluation value is the first value. Determining to use the second cell for transferring the user data if the reference value is lower than 6.
34. A method according to any one of claims 28 to 33. A program for causing a computer to perform a communication control method in a first base station that operates a first cell,
The method
Whether to use the first cell or the second cell operated by the second base station for transferring user data of the mobile station depending on whether or not a predetermined condition is satisfied And determining a bearer setting request for transferring the user data between the core network and the mobile station via the second cell when using the second cell. Sending to
Including the program.

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