JP5334918B2 - Wireless communication system, cell optimization method, server device, and base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a radio communication system capable of reducing a processing load in a base station performing cell adjustment. <P>SOLUTION: A radio communication system comprises: a plurality of evolved node Bs 3 each accommodating a user equipment 4; an MME/GW2 accommodating the evolved node Bs 3; and a SON server 1 grouping the evolved node Bs 3 using a predetermined way to optimize a cell. The SON server 1, when performing a grouping processing of the evolved node Bs 3, selects a master evolved node B for communicating with the MME/GE2 as a representative of the evolved node Bs 3 classified into the same group based on a processing load of each evolved node B 3. The evolved node B 3 selected as the master evolved node B exchanges control information and user data with other evolved node Bs 3 belonging to the same group such that these node Bs 3 transmit the identical downlink signals. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a wireless communication system that performs autonomous cell adjustment.

  In the WiMAX / Advanced WiMAX and LTE / LTE-Advanced systems that make up IMT (International Mobile Telecommunication) and IMT-Advanced, self-optimization of cells is performed using the SON (Self-Organizing Network) function. .

  Cell self-optimization control acquires performance information and control information statistics from mobile stations and base stations using a SON server (SON Server), and controls gateway and base station operations according to control guidelines determined based on this information. Implemented by controlling.

  In 3GPP (3rd Generation Partnership Project), as shown in Non-Patent Document 1, standardization for automatically performing cell optimization is advanced as “Coverage and capacity optimization”.

  In addition, contributions have been issued for standardization, and proposals have been made for measures against coverage fall (dead zone) and cell interference (see Non-Patent Document 2). In Non-Patent Document 2, the transmission power and antenna angle of each base station are determined based on information on success / failure of handover of a mobile station, measurement information (the reception level of the local station and the level of neighboring cells), location information of the mobile station, and the like. It has been proposed to improve the coverage of each base station by adjusting.

3GPP TR36.902 (V9.0.0), 2009-09 “Coverage optimization” 3GPP TSG RAN WG3 R3-080755 31st March-3rd April, 2008

  The conventional SON technology is a cell self-optimization technology for a macro base station, and is trying to realize optimization of cell coverage by adjusting an antenna angle or the like. However, a pico base station or a femto base station constituting a small cell (pico cell or femto cell) that is expected to increase with the introduction of LTE or LTE-Advanced is a cell with a simpler mechanism than a macro base station. Realization of adjustment is desired.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a radio communication system and a cell optimization method capable of reducing a processing load in a base station that performs cell adjustment.

  In order to solve the above-described problems and achieve the object, the present invention provides a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a group of the base stations by a predetermined method. The wireless communication system is configured by a SON server that performs optimization, and the SON server is classified into the same group based on the processing load of each base station when the process of grouping the base stations is performed A master base station that communicates with the gateway device on behalf of the base station is selected, and the base station selected as the master base station is the same from the base station and other base stations belonging to the same group as the base station. Control information and user data are exchanged with the other base station so that a downlink signal is transmitted.

  According to the present invention, the amount of traffic transmitted from a base station other than the master base station to the master base station can be kept low, and the amount of traffic between base stations in a group cell can be optimized. In addition, the number of times of traffic transfer execution within the group cell is kept low, and an increase in processing load due to transfer execution can be prevented.

FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the first embodiment. FIG. 2 is a diagram illustrating a configuration example of a subframe defined by 3GPP LTE. FIG. 3 is a diagram illustrating an operation example of the wireless communication system according to the first embodiment. FIG. 4 is a diagram illustrating an operation example of the wireless communication system according to the first embodiment. FIG. 5 is a diagram illustrating an operation example of the wireless communication system according to the first embodiment. FIG. 6 is a diagram illustrating an operation example of the wireless communication system according to the first embodiment. FIG. 7 is a diagram illustrating an operation example of the wireless communication system according to the first embodiment. FIG. 8 is a diagram showing a process flow of a master base station determination procedure. FIG. 9 is a diagram illustrating an example of base station load information. FIG. 10 is a diagram illustrating a configuration example of a group cell. FIG. 11 is a diagram illustrating an example of base station load information. FIG. 12 is a diagram illustrating a configuration of a radio frame defined by 3GPP LTE. FIG. 13 is a diagram illustrating an example of base station load information.

  Embodiments of a wireless communication system and a cell optimization method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the present embodiment. As shown in the figure, a wireless communication system according to the present embodiment includes an SON server (SON Server) 1, an MME / GW (Mobility Management Entity / Gateway) 2, a plurality of base stations (eNB: evolved Node B) 3, and a mobile device. It consists of a station (UE: User Equipment) 4.

  The SON server 1 includes a SON information collection unit 11 that collects and statistics radio transmission performance, user flow line information, base station load information, and user distribution information, and groups the base stations 4 in the system into a mobile group and an interference group. And a SON group generation unit 12 that generates a CoMP (Coordinated Multipoint) group, and a master base station selection unit 13 that selects a master base station from the grouped base stations.

  The MME / GW 2 includes an MME / GW information collection unit 21 that collects user movement information and user distribution information, and an MME / GW group control unit 22 that performs RAB (Radio Access Bearer) management and highly reliable data transmission processing.

  Each base station 3 has the same configuration, wireless performance measured at the mobile station (referred to as mobile station measured wireless performance), wireless performance measured at the base station (referred to as base station measured wireless performance), and success or failure of handover. Including base station information collection unit 31 that collects received user information such as handover information, base station operation load information, number of accommodated users, etc., and base station transmission control unit 32 that performs transmission control through a radio interface with a mobile station And a base station group control unit 33 for synchronizing access information such as connection information and uplink bandwidth requests between base stations constituting a group cell (details will be described later). The mobile station measurement radio performance and the base station measurement radio performance are collected through radio transmission control between the base station 3 and the mobile station 4. The mobile station measurement radio performance is the downlink radio communication quality, and the base station measurement radio performance is the uplink radio communication quality.

  The mobile station 4 includes a mobile station transmission control unit 41 that performs radio transmission control with the base station 3, and performs handover control information and received power information (RSSI: Received Signal Strength Indicator, CINR: Carrier Interference) through radio transmission control. (Measurement result of noise performance such as Noise Ratio) is notified to the base station.

  In the wireless communication system of the present embodiment configured as described above, information (collected information # 1) collected by the MME / GW information collecting unit 21 of the MME / GE 2 and the base station information collecting unit 31 of the base station 3 are collected. The information collected in step (collected information # 2) is collected in the SON server 1.

  The SON server 1 configuring the wireless communication system that performs autonomous cell adjustment according to the present embodiment is based on information (collected information # 1, # 2) collected from the MME / GW 2 and the base station 3. A plurality of base stations 3 are grouped as necessary to generate a mobile group, an interference group, and a CoMP group. Moreover, the base station 3 forms one cell together with other base stations belonging to the same group. The mobile group is a group of base stations that form a single cell by bundling a plurality of cells in accordance with the flow line (movement) of the user (mobile station 4). An interference group is a group of base stations that form a single cell by bundling a plurality of cells that create strong inter-cell interference. A CoMP group is a group of base stations that form a single cell by bundling a plurality of cells that perform CoMP (multi-point coordination). Hereinafter, a cell formed by bundling the cells of the grouped base stations is referred to as a group cell.

  FIG. 2 is a diagram illustrating a configuration example of a subframe defined by 3GPP LTE (Long Term Evolution). This subframe is used for transmission of user bursts (stores user bursts) data channel area (including part of the synchronization signal), PDCCH (Physical Downlink Control Channel) that stores user burst mapping information, and feedback. A control channel region including a PCFICH (Physical Control Format Indicator Channel) for transmitting information and a PHICH (Physical Hybrid ARQ Indicator Channel) for transmitting HARQ (Hybrid ARQ) acknowledgment information.

  In the radio communication system according to the present embodiment, a specific base station among base stations constituting a group cell operates as a master base station, and information on the control channel area and data channel area shown in FIG. It is set to be the same between base stations (the same downlink signal is transmitted from each base station in the group). That is, in the group cell formed by the base stations grouped by the SON group generation unit 12, the mobile station 4 can acquire the same control channel information regardless of the cell in the group cell. . As a result, the coverage area can be expanded by the diversity effect in addition to making the control channel region interference-free.

  Hereinafter, the operation of the wireless communication system according to the present embodiment will be described with reference to FIGS. 3-7 is a figure which shows the operation example of the radio | wireless communications system of this Embodiment.

<Operation when transmitting control information generated by master base station in group cell>
FIG. 3 shows an operation example when one of a plurality of base stations 3 constituting a group cell is set as a master. Specifically, control information that can be controlled only by the base station 3 such as broadcast information. Shows the operation when the base station in the group cell is transmitted to the radio section. In FIG. 3, for convenience of explanation, the grouped base stations are referred to as base stations 3a to 3d, and the components are also distinguished by adding a to d. In addition, only components that are directly related to the operation to be described are described. The same applies to FIGS. 4 to 7. For simplicity, only one mobile station is shown, but usually there are a plurality.

  In the operation example shown in FIG. 3, the base station 3a operates as a master. That is, the base station transmission control unit 32a of the base station 3a generates control information 101 common to the base stations in the group, and notifies this control information 101 to the base station group control unit 33a together with the transmission timing. Further, the base station transmission control unit 32a stores the control information 101 in the control channel region (see FIG. 2) of the subframe according to the notified transmission timing, and transmits it to the radio section (in the cell).

  The base station group control unit 33a that has received the control information 101 and the transmission timing information from the base station transmission control unit 32a receives the base station group control units 33b, 33c of the other base stations 3b, 3c, 3d constituting the group cell. , 33d, information received from the base station transmission control unit 32a (control information 101 and transmission timing information) is transmitted.

  The base station group control units 33b, 33c, 33d of the base stations 3b, 3c, 3d pass the information received from the base station group control unit 33a to the base station transmission control units 32b, 32c, 32d, and the base station transmission control unit 32b , 32c, and 32d transmit the received control information 101 to the radio section at a designated timing (a transmission timing indicated by information received from the base station group control unit 33a).

<Operation when base station configuring group cell receives control information from mobile station>
FIG. 4 is a diagram illustrating an operation example when the base station configuring the group cell receives control information from a subordinate mobile station, and the operation when the base station 3 d receives control information from the mobile station 4. Is shown. As in FIG. 3, it is assumed that the base station 3a is a master base station.

  When the control information 102 transmitted from the mobile station 4 is received, the base station transmission control unit 32d of the base station 3d transmits the control information 102 to the master base station (base station 3a) via the base station group control unit 33d.

  In the base station 3a, the base station group control unit 33a receives the control information 102 transmitted from the base station 3d, and passes this control information 102 to the base station transmission control unit 32a. The base station transmission control unit 32a executes processing according to the contents of the received control information 102 and generates control information 103 as a response. Then, the control information 103 is notified to the base station group control unit 33a together with the transmission timing. Further, the base station transmission control unit 32a transmits the control information 103 to the radio section according to the notified transmission timing.

  The base station group control unit 33a, which has received the control information 103 and the transmission timing information from the base station transmission control unit 32a, transmits the control information 103 and other base stations 3b, 3c, 3d constituting the transmission timing information group cell. To the base station group control units 33b, 33c and 33d. The base station group control units 33b, 33c, 33d of the base stations 3b, 3c, 3d that have received this information pass the information received from the base station group control unit 33a to the base station transmission control units 32b, 32c, 32d. The station transmission control units 32b, 32c, and 32d transmit the received control information 103 to the radio section at a designated timing (a transmission timing indicated by information received from the base station group control unit 33a).

<Operation when base station constituting group cell receives allocation request for uplink data transmission band>
FIG. 5 is a diagram showing an operation example when the base station constituting the group cell receives an uplink bandwidth allocation request from a subordinate mobile station, and the base stations 3c and 3d receive user data from the mobile station 4. The operation when an upstream bandwidth request for transmitting is received is shown. As in FIG. 3, it is assumed that the base station 3a is a master base station.

  When receiving the upstream bandwidth request 104 transmitted from the mobile station 4, the base station transmission control unit 32d of the base station 3d sends the upstream bandwidth request 104 to the master base station (base station 3a) via the base station group control unit 33d. To transmit. Similarly, the base station transmission control unit 32c of the base station 3c that has received the same upstream bandwidth request 104 received by the base station 3d transmits the upstream bandwidth request 104 to the base station 3a via the base station group control unit 33c. .

  The base station group control unit 33a of the base station 3a that has received the upstream bandwidth request 104 from the base stations 3c and 3d passes each received upstream bandwidth request 104 to the base station transmission control unit 32a. The base station transmission control unit 32a confirms the two received upstream bandwidth requests 104, determines that these are upstream bandwidth requests 104 from one mobile station 4, and processes them as one upstream bandwidth request. Further, it also processes the uplink bandwidth request of other mobile stations 4 notified from the base station in the group cell including itself, and generates a response signal 105 for each mobile station 4. The response signal 105 is notified to the base station group control unit 33a together with the transmission timing.

  Thereafter, the response signal 105 and its transmission timing are transmitted from the base station group control unit 33a to the base station transmission control units 32b, 32c, and 32d via the base station group control units 33b, 33c, and 33d of other base stations. The base station transmission control units 32b, 32c, and 32d transmit the response signal 105 to the radio section at a timing specified by the base station transmission control unit 32a. Further, the base station transmission control unit 32a transmits the response signal 105 to the radio section according to the notified transmission timing.

<Operation when uplink user data is received from a mobile station constituting a group cell>
FIG. 6 is a diagram illustrating an operation example when the base station configuring the group cell receives user data from the mobile station. When the base stations 3c and 3d receive user data from the mobile station 4, FIG. The operation is shown. As in FIG. 3, it is assumed that the base station 3a is a master base station.

  When the user data 106 transmitted from the mobile station 4 is received, the base station transmission control unit 32d of the base station 3d transmits the user data 106 to the master base station (base station 3a) via the base station group control unit 33d. . Similarly, the base station transmission control unit 32c of the base station 3c that has received the same user data 106 received by the base station 3d transmits the uplink bandwidth request 104 to the base station 3a via the base station group control unit 33c. At this time, the base stations 3 c and 3 d that have directly received the user data 106 from the mobile station 4 do not perform a delivery confirmation process for the received user data 106.

  The base station group control unit 33a of the base station 3a that has received the user data 106 from the base stations 3c and 3d passes each received user data 106 to the base station transmission control unit 32a. The base station transmission control unit 32a performs processing on the received two user data 106, transfers the user data 106 to the PDCP 34a, and generates a delivery confirmation 107 for the received user data 106. Then, this delivery confirmation 107 is notified to the base station group control unit 33a together with the transmission timing. Further, the base station transmission control unit 32a transmits the delivery confirmation 107 to the radio section according to the notified transmission timing.

  The PDCP 34a, which is omitted in FIG. 1, is a component that provides the PDCP function, and transfers the user data 106 received from the base station transmission control unit 32a to the MME / GW 2. In addition, the base station group control unit 33a sends a delivery confirmation 107 to be transmitted and its transmission timing to the base station group control units 33b, 33c, and 33d of the other base stations 3b, 3c, and 3d configuring the group cell ( Transmission timing information). The base station group control units 33b, 33c, 33d of the base stations 3b, 3c, 3d pass the delivery confirmation 107 and the transmission timing to the base station transmission control units 32b, 32c, 32d, and the base station transmission control units 32b, 32c, 32d transmits the delivery confirmation 107 to the radio section at the designated timing. The PDCP 34a may be included in the base station transmission control unit 32a.

<Operation when transmitting downlink user data in a group cell>
FIG. 7 is a diagram illustrating an operation example when transmitting downlink user data in a group cell, and illustrates an operation when the mobile station 4 receives user data from the base stations 3c and 3d. As in FIG. 3, it is assumed that the base station 3a is a master base station.

  The MME / GW 2 transmits user data 108 to the master base station 3a. In the base station 3a, the PDCP 34a receives the user data 108 transmitted from the MME / GW 2 and transmits it to the base station transmission control unit 32a. The base station transmission control unit 32a notifies the base station group control unit 33a of the user data 108 received from the PDCP 34a and its transmission timing. Further, the user data 108 is transmitted to the radio section according to the transmission timing notified to the base station group control unit 33a.

  The base station group control unit 33a transmits user data 108 to be transmitted and its transmission timing to the base station group control units 33b, 33c, and 33d of the other base stations 3b, 3c, and 3d configuring the group cell. . The base station group controllers 33b, 33c, 33d of the base stations 3b, 3c, 3d pass the user data 108 and its transmission timing to the base station transmission controllers 32b, 32c, 32d, and the base station transmission controllers 32b, 32c, 32d transmits the user data 108 to the mobile station 4 to the radio section at the designated timing.

  Here, consider which base station is the most efficient among a plurality of base stations. In each operation described with reference to FIGS. 3 to 7, processing is concentrated on the master base station 3 a and the load increases. Further, since the upstream information (information from the mobile station) is aggregated in the master base station 3a, the traffic amount addressed to the base station 3a increases.

  In the case of the operation shown in FIG. 3, there is no difference in processing load between the base stations regardless of which of the base stations 3a to 3d becomes the master. That is, regardless of which base station becomes the master, the difference in processing load between the master base station and other base stations is constant. In addition, there is no difference in the amount of traffic between base stations.

  Further, in the case of the operation shown in FIG. 4, the master base station 3a processes the control signal transmitted from all the mobile stations 4 in the group cell. It does not change even if it becomes. However, since the control signal from the mobile station 4 is concentrated on the base station 3a serving as a master, the base station 3a directly receives the control signal from the mobile station 4 between the base stations in the group cell. The amount of control message traffic can be reduced. The operation shown in FIG. 5 is the same as the operation shown in FIG.

  Further, in the case of FIG. 6 as well, in the same manner as in the case of the operation shown in FIG. 4, the master base station 3 a receives the user data from the mobile station 4 directly. It is possible to reduce the amount of user data traffic.

  In the case of the operation shown in FIG. 7, as in the case of the operation shown in FIG. 3, no matter which base station among the base stations 3a to 3d becomes the master, the processing load between the base stations, and the base station There is no difference in traffic volume between the two.

  From the above, the base station that is the master among the base station group in the group cell can be the base station 3 that receives the control signal from the mobile station 4 and the amount of user data that is the largest among the group cells. The amount of traffic can be reduced. Therefore, in the wireless communication system of the present embodiment, the master base station selection unit 13 (see FIG. 1) of the SON server 1 determines a master base station according to the following procedure.

  FIG. 8 is a diagram illustrating a process flow of a master base station determination procedure. As shown in the figure, in the wireless communication system of the present embodiment, first, the SON information collection unit 11 detects a group cell generation trigger, and instructs the SON group generation unit 12 to generate a group cell (grouping of base stations). (Step S1). The group cell generation trigger is not particularly defined. Any method may be used. For example, trigger detection (group cell generation start determination) may be performed based on the number of mobile stations accommodated in the system, the number of times of handover execution, the measurement result of inter-cell interference, and the like.

  Next, the SON group generation unit 12 performs grouping according to a generation trigger type (group generation type: movement / interference / CoMP) notified when a group cell generation instruction is received from the SON information collection unit 11, The converted base station group is notified to the master base station selection unit 13 (step S2).

  The master base station selection unit 13 acquires the load state (base station load information) of each base station of the notified base station group from the SON information collection unit 11 (step S3), and based on the acquired base station load information The master base station is selected, and the selection result is notified to the SON group generation unit 12 (step S4).

  The SON group generation unit 12 notifies each base station of the base station group constituting the group cell of the base station that constitutes the group and the base station that is the master among them, and instructs the formation of the group cell (step S5). .

  In addition, although the example in the case of providing the independent component (master base station selection part 13) for selecting a master base station was shown in FIG. 1, the SON group production | generation part 12 implements selection of a master base station. You may make it do.

  FIG. 9 is a diagram illustrating an example of base station load information held by the SON information collection unit 11. The master base station selection unit 13 acquires the base station load information illustrated in FIG. 9 as the load information of each base station of the base station group notified from the SON group generation unit 12 in the processing of steps S3 and S4 described above. In this case, it is determined that the uplink control message and the uplink data processing load is high in the base station 3a, the base station 3a is selected as the master, and the base station 3 constituting the group cell is notified. This makes it possible to optimize the traffic amount between base stations in the group cell.

  As described above, in the radio communication system according to the present embodiment, when selecting a master base station from base stations forming a group cell, the SON server selects based on the processing load of each base station in the group. It was decided. Specifically, the base station with the largest traffic volume directly received from the mobile station is selected. As a result, the amount of traffic transmitted from a base station other than the master base station to the master base station can be kept low, and the amount of traffic between base stations in the group cell can be optimized. In addition, the number of times traffic is transferred in the group cell can be kept low, and the processing load can be prevented from increasing with the transfer.

  In this embodiment, the case where the master base station is selected by the master base station selecting unit 13 of the SON server 1 has been described. However, the load status is notified between the grouped base stations, and the base station A master base station may be determined between them.

  In addition, the master base station may be changed as appropriate in accordance with a change in processing load at each base station.

Embodiment 2. FIG.
Next, the radio communication system according to the second embodiment will be described. The system configuration is the same as that of the first embodiment (see FIG. 1).

  In the first embodiment, the case where one base station 3 in the group cell is used as a master has been described. In this case, the load on the master base station increases. Here, transmission of control information that can be controlled only by the base station 3, such as broadcast information of the control channel described with reference to FIG. 3 (control information broadcast in the cell that does not require a response from the mobile station) It is possible to process the control messages and user data transmitted / received to / from the mobile station 4 shown in FIGS. 4 to 7 independently of each other. Further, as shown in the first embodiment, the processing of control information that can be controlled only by the base station 3 can be performed regardless of the processing load and traffic volume between base stations, regardless of which base station 3 in the group cell performs. There is no difference.

  Therefore, in the wireless communication system of the present embodiment, when determining the master base station, the master base station selection unit 13 of the SON server 1 confirms the base station load information held in the SON information collection unit 7, The base station with the lowest processing load is selected as the master base station in the control information transmission processing operation (operation shown in FIG. 3) that can be controlled only by the base station, such as broadcast information of the control channel. Also, the master base station in other operations (the operations shown in FIGS. 4 to 7) selects the base station with the largest traffic volume directly received from the mobile station, as in the first embodiment. For example, when the base station load information at the time of determining the master base station is as shown in FIG. 9, the master base station in the control information transmission processing operation that can be controlled only by the base station is defined as the base station 3b, The master base station in operation is defined as a base station 3a.

  Thus, in this embodiment, the master base station in the control information transmission operation that can be controlled only by the base station is assigned to the base station with the lowest processing load. Thereby, the traffic amount between the base stations in the group cell can be optimized, and the load concentrated on one base station can be distributed.

  In this embodiment, the master base station is selected by the master base station selection unit 13 of the SON server 1, but the load status is notified between the grouped base stations, and only the base station 3 is selected. A master base station that performs processing of control information (control channel broadcast information shown in FIG. 3 and the like) that can be controlled by the mobile station and a master base station that transmits and receives control information and user data to and from the mobile station may be determined.

Embodiment 3 FIG.
Next, the radio communication system according to the third embodiment will be described. The system configuration is the same as that of the first embodiment (see FIG. 1).

  In the second embodiment, the master base station in the case of processing control information (such as control channel broadcast information) that can be controlled only by the base station 3 and the master base station that performs other operations are set to different base stations. To distribute the processing load. However, the processing of control information that can be controlled only by the base station 3 is generally less loaded than the processing of upstream control messages and upstream data, and the master that processes upstream control messages and upstream data is the base station 3a. The load is high. Therefore, in the present embodiment, a case will be described in which the load is distributed by setting a plurality of base stations as master base stations in the operations of FIGS. 3 to 7 shown in the first embodiment. In the following description, a case where there are two master base stations is shown, but three or more master base stations may be used.

  FIG. 10 is a diagram illustrating a configuration example of a group cell, in which six cells 30a, 30b, 30c, 30d, 30e, and 30f each configured by the base stations 3a, 3b, 3c, 3d, 3e, and 3f are group cells. Is shown.

  FIG. 11 is a diagram showing an example of base station load information held by the SON information collection unit 11. According to the base station load information shown in FIG. 11, since the load factor of the base station 3a and the base station 3f is high, the two base stations process uplink control messages and uplink data (shown in FIGS. 4 to 7). Candidates of master base stations that perform each operation) in a distributed manner.

  FIG. 12 is a diagram illustrating a configuration of a radio frame defined by 3GPP LTE. For both uplink and downlink, one radio frame is 10 ms, and is composed of 10 1 ms subframes. In the present embodiment, 3GPP LTE will be described as an example. When the base stations 3a and 3f operate as master base stations, for example, the base station 3a processes subframe # 0 to subframe # 4 in FIG. 12 as a master, and subframe # 5 to subframe # 4. 9 is processed by the base station 3f as a master. Each base station in the group cell determines which of the two masters to transfer to the base station 3a or 3f depending on which subframe the uplink bandwidth request from the mobile station 4 is received.

  However, exceptions are allowed. For example, the mobile station 4 located in the vicinity of the boundary between the cell 30f of the base station 3f and the cell 30e of the base station 3e has an upstream bandwidth in subframes # 0 to # 4 that the base station 3a is to process. When the request is notified, the base station 3e and 3f may receive the uplink allocation request. At this time, if normal, the base station 3e notifies the base station 3a of an upstream bandwidth request. That is, although the mobile station 4 can directly transmit / receive data to / from the master base station 3f, the mobile station 4 transmits / receives data using the base station 3a as a master, and wasteful traffic between base stations in the group cell. Will be generated. Therefore, when the master base station 3f receives an uplink allocation request from the mobile station 4 at a timing that is not managed by the master base station 3f, the master base station 3f notifies the base station 3a that it will manage subsequent data transmission / reception using its own resources. Then, the uplink bandwidth request processing of the mobile station 4 notified from the base station 3e to the base station 3a is stopped. Thereby, transfer of unnecessary user data between subsequent base stations can be suppressed.

  Note that, when selecting a plurality of master base stations, if the plurality of master base stations receive an upstream bandwidth request from the same mobile station 4, the above-described processing becomes inconsistent. A base station that does not receive data from 4 is selected (considering that the cells of the master base station do not overlap with each other so that adjacent base stations are not selected). When selecting two master base stations, the master base station selection unit 13 selects, for example, the base station with the highest processing load as the first master base station, and then adjoins the first master base station. The base station with the highest processing load is selected as the second master base station. When selecting three or more stations, after selecting the second master base station, it is only necessary to additionally select the base station with the highest processing load among the base stations not adjacent to any of the selected base stations. .

  Further, the master base station selection unit 13 determines which section of the base stations 3a and 3f operates as the master base station.

  As described above, the master base stations 3a and 3f allocate their own management target resources to the upstream bandwidth request notified to them via other base stations and the upstream bandwidth request received directly from the mobile station. Thereafter, the processing of the uplink control message, the processing of the uplink data, and the processing of the downlink data are performed, and the transmission data and the transmission timing are notified to the base station in the group cell.

  As described above, in the radio communication system according to the present embodiment, the resources managed by each master base station are clearly separated, for example, by switching the base station that operates as the master base station within one radio frame. As described in the previous embodiment, the amount of traffic between base stations in the group cell can be optimized, and the uplink control message and uplink data can be optimized. The processing load can be distributed to a plurality of base stations.

  As in the second embodiment, the master base station for processing control information that can be controlled only by the base station may be set to the base station with the lowest processing load.

  In this embodiment, an example in which the master base station is switched in units of 3GPP LTE subframes has been described. However, resources are divided on the frequency axis or time axis in the subframe, and each resource is assigned to a different master base. You may comprise so that a station may handle. Also, it is not specialized for LTE.

Embodiment 4 FIG.
Next, the radio communication system according to the fourth embodiment will be described. The system configuration is the same as that of the first embodiment (see FIG. 1).

  FIG. 13 is a diagram illustrating an example of base station load information held by the SON information collection unit 11. According to the base station load information shown in FIG. 13, since the load factor of the base station 3a and the base station 3d is high, these two base stations are candidates for the master base station.

  Here, if the configuration of the group cell is as shown in FIG. 10, the base station 3a and the base station 3d are adjacent to each other. Therefore, when the control described in the third embodiment is applied, inconsistency may occur. . Therefore, of the base stations 3a and 3d, the base station 3d with the low load factor is excluded from the candidates, and the base station 3f with the next highest load is the candidate. However, in this case, the load factor of the base station 3a is twice that of 3f, and the processing load (load factor) of both is greatly different. Therefore, in the radio communication system according to the present embodiment, when there is a difference in the load factor of the master base station, the master base station selection unit 13 considers the ratio of the load to the resource shared by the master base station selection unit 13. Distribute more resources to the higher. This makes it possible to use resources more efficiently.

  As described above, the wireless communication system according to the present invention is useful as a system having a function of performing cell optimization and forming one cell by a plurality of base stations, and in particular, a plurality of small base stations ( This is suitable for a radio communication system in which one cell is formed by a pico base station or a femto base station.

1 SON Server
2 MME / GW
3, 3a, 3b, 3c, 3d, 3e, 3f Base station (eNB)
4 Mobile station (UE)
DESCRIPTION OF SYMBOLS 11 SON information collection part 12 SON group production | generation part 13 Master base station selection part 21 MME / GW information collection part 22 MME / GW group control part 31 Base station information collection part 30a, 30b, 30c, 30d, 30e, 30f Cell 32, 32a, 32b, 32c, 32d Base station transmission control unit 33, 33a, 33b, 33c, 33d Base station group control unit 34a PDCP
41 Mobile station transmission controller

Claims (12)

A wireless communication system including a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a SON server that groups the base stations in a predetermined method to optimize cells,
As the master base station that communicates with the gateway device on behalf of the base stations classified into the same group based on the processing load of each base station, when the SON server performs the process of grouping the base stations , Select the base station with the largest processing load ,
The base station selected as the master base station is controlled with the other base station so that the same downlink signal is transmitted from the base station and another base station belonging to the same group as the own station. A wireless communication system characterized in that information and user data are exchanged. A wireless communication system including a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a SON server that groups the base stations in a predetermined method to optimize cells,
When the processing for grouping the base stations is performed, the SON server selects a master base station that communicates with the gateway device on behalf of the base stations classified into the same group based on the processing load of each base station. And
The base station selected as the master base station is controlled with the other base station so that the same downlink signal is transmitted from the base station and another base station belonging to the same group as the own station. Information and user data will be exchanged,
The SON server selects a base station with the smallest processing load as the first master base station, and further selects a base station with the largest processing load as the second master base station,
The base station selected as the first master base station exchanges control information broadcast in the cell with another base station belonging to the same group as the own station. The second master base A base station selected as a station exchanges control information and user data other than control information broadcast in the cell with another base station belonging to the same group as the own station. radio communications system that. A wireless communication system including a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a SON server that groups the base stations in a predetermined method to optimize cells,
When the processing for grouping the base stations is performed, the SON server selects a master base station that communicates with the gateway device on behalf of the base stations classified into the same group based on the processing load of each base station. And
The base station selected as the master base station is controlled with the other base station so that the same downlink signal is transmitted from the base station and another base station belonging to the same group as the own station. Information and user data will be exchanged,
The SON server selects two or more base stations including a base station with the maximum processing load as a master base station, and further, each period overlaps each period in which each selected base station operates as a master base station. Decide not to,
Wherein each base station is selected as the master base station, the SON server is determined by, radio communications systems that characterized by operating as the master base station period, in which the self station operates as a master base station. When selecting the master base station, the SON server first selects the base station with the largest processing load as the master base station, and then processes the base station not adjacent to the base station selected as the master base station. A process of additionally selecting a base station with the largest load as a master base station, and subsequently selecting a base station with the largest processing load as a master base station among base stations not adjacent to a base station that has already been selected as a master base station The wireless communication system according to claim 3 , wherein the number of master base stations is repeated until a desired number is reached. The SON server, when determining each period during which each selected base station operates as a master base station, determines the length of each period based on the processing load of each selected base station. Item 5. The wireless communication system according to Item 3 or 4 . The wireless communication system according to any one of claims 1 to 5, wherein the another base station transfers control information and user data from a mobile station accommodated to the master base station. Cell optimization executed in a radio communication system composed of a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a SON server that groups the base stations by a predetermined method to optimize cells A method of
An information collecting step in which the SON server collects statistical information used in cell optimization processing from the base station and the gateway device;
The SON server groups the base stations based on the collected statistical information, and further communicates with the gateway device on behalf of the base stations classified into the same group based on the processing load of each base station. A grouping step of selecting a base station with the largest processing load as a master base station to be
Including
The base station selected as the master base station is controlled with the other base station so that the same downlink signal is transmitted from the base station and another base station belonging to the same group as the own station. A cell optimization method characterized by passing information and user data. Cell optimization executed in a radio communication system composed of a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a SON server that groups the base stations by a predetermined method to optimize cells A method of
An information collecting step in which the SON server collects statistical information used in cell optimization processing from the base station and the gateway device;
The SON server groups the base stations based on the collected statistical information, and further communicates with the gateway device on behalf of the base stations classified into the same group based on the processing load of each base station. A grouping step for selecting a master base station to perform;
Including
The base station selected as the master base station is controlled with the other base station so that the same downlink signal is transmitted from the base station and another base station belonging to the same group as the own station. Information and user data will be exchanged,
In the grouping step, the base station with the smallest processing load is selected as the first master base station, and the base station with the largest processing load is selected as the second master base station,
The base station selected as the first master base station exchanges control information broadcast in the cell with another base station belonging to the same group as the own station. A base station selected as a base station exchanges control information and user data other than the control information broadcast in the cell with another base station belonging to the same group as the own station. Ruse Le optimization methods to the. Cell optimization executed in a radio communication system composed of a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a SON server that groups the base stations by a predetermined method to optimize cells A method of
An information collecting step in which the SON server collects statistical information used in cell optimization processing from the base station and the gateway device;
The SON server groups the base stations based on the collected statistical information, and further communicates with the gateway device on behalf of the base stations classified into the same group based on the processing load of each base station. A grouping step for selecting a master base station to perform;
Including
The base station selected as the master base station is controlled with the other base station so that the same downlink signal is transmitted from the base station and another base station belonging to the same group as the own station. Information and user data will be exchanged,
In the grouping step, two or more base stations including a base station having the maximum processing load are selected as master base stations, and each period in which each selected base station operates as a master base station Decide not to overlap,
Wherein each base station is selected as a master base station has been determined in the grouping step, the period of the own station operates as a master base station, features and to Rousset Le optimized to operate as a master base station in Method. In the grouping step, when each period in which each selected base station operates as a master base station is determined, the length of each period is determined based on the processing load of each selected base station. The cell optimization method according to claim 9 . As the SON server of a wireless communication system including a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a SON server that optimizes cells by grouping the base stations by a predetermined method An operating server device,
  When performing the process of grouping the base stations, as a master base station that communicates with the gateway device on behalf of the base stations classified into the same group based on the processing load of each base station, the processing load is the largest Select a base station, and send the same downlink signal to the selected base station from the base station and other base stations belonging to the same group as the local station. Instruct to pass control information and user data
  The server apparatus characterized by the above-mentioned. In the base station of a wireless communication system configured by a plurality of base stations that accommodate mobile stations, a gateway device that accommodates base stations, and a SON server that optimizes cells by grouping the base stations by a predetermined method There,
  In the grouping process of base stations by the SON server, when the processing load is determined to be maximum in the same group and selected as a master base station that communicates with the gateway device on behalf of the group,
  Control information and user data are exchanged with the other base station so that the same downlink signal is transmitted from the own station and another base station belonging to the same group as the own station.
  A base station characterized by that.